diff --git a/src/inc/til.h b/src/inc/til.h
index fce071cf1..1519f9245 100644
--- a/src/inc/til.h
+++ b/src/inc/til.h
@@ -6,6 +6,7 @@
 #include "til/at.h"
 #include "til/color.h"
 #include "til/some.h"
+#include "til/size.h"
 #include "til/u8u16convert.h"
 
 namespace til // Terminal Implementation Library. Also: "Today I Learned"
diff --git a/src/inc/til/size.h b/src/inc/til/size.h
new file mode 100644
index 000000000..f996c9325
--- /dev/null
+++ b/src/inc/til/size.h
@@ -0,0 +1,265 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+#pragma once
+
+#ifdef UNIT_TESTING
+class SizeTests;
+#endif
+
+namespace til // Terminal Implementation Library. Also: "Today I Learned"
+{
+    class size
+    {
+    public:
+        constexpr size() noexcept :
+            size(0, 0)
+        {
+        }
+
+        // On 64-bit processors, int and ptrdiff_t are different fundamental types.
+        // On 32-bit processors, they're the same which makes this a double-definition
+        // with the `ptrdiff_t` one below.
+#if defined(_M_AMD64) || defined(_M_ARM64)
+        constexpr size(int width, int height) noexcept :
+            size(static_cast<ptrdiff_t>(width), static_cast<ptrdiff_t>(height))
+        {
+        }
+#endif
+
+        size(size_t width, size_t height)
+        {
+            THROW_HR_IF(E_ABORT, !base::MakeCheckedNum(width).AssignIfValid(&_width));
+            THROW_HR_IF(E_ABORT, !base::MakeCheckedNum(height).AssignIfValid(&_height));
+        }
+
+        constexpr size(ptrdiff_t width, ptrdiff_t height) noexcept :
+            _width(width),
+            _height(height)
+        {
+        }
+
+        // This template will convert to size from anything that has an X and a Y field that appear convertable to an integer value
+        template<typename TOther>
+        constexpr size(const TOther& other, std::enable_if_t<std::is_integral_v<decltype(std::declval<TOther>().X)> && std::is_integral_v<decltype(std::declval<TOther>().Y)>, int> /*sentinel*/ = 0) :
+            size(static_cast<ptrdiff_t>(other.X), static_cast<ptrdiff_t>(other.Y))
+        {
+        }
+
+        // This template will convert to size from anything that has a cx and a cy field that appear convertable to an integer value
+        template<typename TOther>
+        constexpr size(const TOther& other, std::enable_if_t<std::is_integral_v<decltype(std::declval<TOther>().cx)> && std::is_integral_v<decltype(std::declval<TOther>().cy)>, int> /*sentinel*/ = 0) :
+            size(static_cast<ptrdiff_t>(other.cx), static_cast<ptrdiff_t>(other.cy))
+        {
+        }
+
+        constexpr bool operator==(const size& other) const noexcept
+        {
+            return _width == other._width &&
+                   _height == other._height;
+        }
+
+        constexpr bool operator!=(const size& other) const noexcept
+        {
+            return !(*this == other);
+        }
+
+        size operator+(const size& other) const
+        {
+            ptrdiff_t width;
+            THROW_HR_IF(E_ABORT, !base::CheckAdd(_width, other._width).AssignIfValid(&width));
+
+            ptrdiff_t height;
+            THROW_HR_IF(E_ABORT, !base::CheckAdd(_height, other._height).AssignIfValid(&height));
+
+            return size{ width, height };
+        }
+
+        size operator-(const size& other) const
+        {
+            ptrdiff_t width;
+            THROW_HR_IF(E_ABORT, !base::CheckSub(_width, other._width).AssignIfValid(&width));
+
+            ptrdiff_t height;
+            THROW_HR_IF(E_ABORT, !base::CheckSub(_height, other._height).AssignIfValid(&height));
+
+            return size{ width, height };
+        }
+
+        size operator*(const size& other) const
+        {
+            ptrdiff_t width;
+            THROW_HR_IF(E_ABORT, !base::CheckMul(_width, other._width).AssignIfValid(&width));
+
+            ptrdiff_t height;
+            THROW_HR_IF(E_ABORT, !base::CheckMul(_height, other._height).AssignIfValid(&height));
+
+            return size{ width, height };
+        }
+
+        size operator/(const size& other) const
+        {
+            ptrdiff_t width;
+            THROW_HR_IF(E_ABORT, !base::CheckDiv(_width, other._width).AssignIfValid(&width));
+
+            ptrdiff_t height;
+            THROW_HR_IF(E_ABORT, !base::CheckDiv(_height, other._height).AssignIfValid(&height));
+
+            return size{ width, height };
+        }
+
+        size divide_ceil(const size& other) const
+        {
+            // Divide normally to get the floor.
+            const size floor = *this / other;
+
+            ptrdiff_t adjWidth = 0;
+            ptrdiff_t adjHeight = 0;
+
+            // Check for width remainder, anything not 0.
+            // If we multiply the floored number with the other, it will equal
+            // the old width if there was no remainder.
+            if (other._width * floor._width != _width)
+            {
+                // If there was any remainder,
+                // Grow the magnitude by 1 in the
+                // direction of the sign.
+                if (floor.width() >= 0)
+                {
+                    ++adjWidth;
+                }
+                else
+                {
+                    --adjWidth;
+                }
+            }
+
+            // Check for height remainder, anything not 0.
+            // If we multiply the floored number with the other, it will equal
+            // the old width if there was no remainder.
+            if (other._height * floor._height != _height)
+            {
+                // If there was any remainder,
+                // Grow the magnitude by 1 in the
+                // direction of the sign.
+                if (_height >= 0)
+                {
+                    ++adjHeight;
+                }
+                else
+                {
+                    --adjHeight;
+                }
+            }
+
+            return floor + size{ adjWidth, adjHeight };
+        }
+
+        constexpr ptrdiff_t width() const noexcept
+        {
+            return _width;
+        }
+
+        template<typename T>
+        T width() const
+        {
+            T ret;
+            THROW_HR_IF(E_ABORT, !base::MakeCheckedNum(width()).AssignIfValid(&ret));
+            return ret;
+        }
+
+        constexpr ptrdiff_t height() const noexcept
+        {
+            return _height;
+        }
+
+        template<typename T>
+        T height() const
+        {
+            T ret;
+            THROW_HR_IF(E_ABORT, !base::MakeCheckedNum(height()).AssignIfValid(&ret));
+            return ret;
+        }
+
+        ptrdiff_t area() const
+        {
+            ptrdiff_t result;
+            THROW_HR_IF(E_ABORT, !base::CheckMul(_width, _height).AssignIfValid(&result));
+            return result;
+        }
+
+#ifdef _WINCONTYPES_
+        operator COORD() const
+        {
+            COORD ret;
+            THROW_HR_IF(E_ABORT, !base::MakeCheckedNum(_width).AssignIfValid(&ret.X));
+            THROW_HR_IF(E_ABORT, !base::MakeCheckedNum(_height).AssignIfValid(&ret.Y));
+            return ret;
+        }
+#endif
+
+#ifdef _WINDEF_
+        operator SIZE() const
+        {
+            SIZE ret;
+            THROW_HR_IF(E_ABORT, !base::MakeCheckedNum(_width).AssignIfValid(&ret.cx));
+            THROW_HR_IF(E_ABORT, !base::MakeCheckedNum(_height).AssignIfValid(&ret.cy));
+            return ret;
+        }
+#endif
+
+#ifdef DCOMMON_H_INCLUDED
+        constexpr operator D2D1_SIZE_F() const noexcept
+        {
+            return D2D1_SIZE_F{ gsl::narrow_cast<float>(_width), gsl::narrow_cast<float>(_height) };
+        }
+#endif
+
+    protected:
+        ptrdiff_t _width;
+        ptrdiff_t _height;
+
+#ifdef UNIT_TESTING
+        friend class ::SizeTests;
+#endif
+    };
+};
+
+#ifdef __WEX_COMMON_H__
+namespace WEX::TestExecution
+{
+    template<>
+    class VerifyOutputTraits<::til::size>
+    {
+    public:
+        static WEX::Common::NoThrowString ToString(const ::til::size& size)
+        {
+            return WEX::Common::NoThrowString().Format(L"[W:%td, H:%td]", size.width(), size.height());
+        }
+    };
+
+    template<>
+    class VerifyCompareTraits<::til::size, ::til::size>
+    {
+    public:
+        static bool AreEqual(const ::til::size& expected, const ::til::size& actual) noexcept
+        {
+            return expected == actual;
+        }
+
+        static bool AreSame(const ::til::size& expected, const ::til::size& actual) noexcept
+        {
+            return &expected == &actual;
+        }
+
+        static bool IsLessThan(const ::til::size& expectedLess, const ::til::size& expectedGreater) = delete;
+
+        static bool IsGreaterThan(const ::til::size& expectedGreater, const ::til::size& expectedLess) = delete;
+
+        static bool IsNull(const ::til::size& object) noexcept
+        {
+            return object == til::size{};
+        }
+    };
+};
+#endif
diff --git a/src/til/precomp.h b/src/til/precomp.h
index 6e68de7f6..2375e15ec 100644
--- a/src/til/precomp.h
+++ b/src/til/precomp.h
@@ -25,7 +25,17 @@ Abstract:
 // Windows Header Files:
 #include <windows.h>
 
+#define BLOCK_TIL
 // This includes support libraries from the CRT, STL, WIL, and GSL
 #include "LibraryIncludes.h"
 
+#include "WexTestClass.h"
+
+// Include DirectX common structures so we can test them.
+// (before TIL so its support lights up)
+#include <dcommon.h>
+
+// Include TIL after Wex to get test comparators.
+#include "til.h"
+
 // clang-format on
diff --git a/src/til/ut_til/SizeTests.cpp b/src/til/ut_til/SizeTests.cpp
new file mode 100644
index 000000000..09b573698
--- /dev/null
+++ b/src/til/ut_til/SizeTests.cpp
@@ -0,0 +1,494 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+#include "precomp.h"
+
+#include "til/size.h"
+
+using namespace WEX::Common;
+using namespace WEX::Logging;
+using namespace WEX::TestExecution;
+
+class SizeTests
+{
+    TEST_CLASS(SizeTests);
+
+    TEST_METHOD(DefaultConstruct)
+    {
+        const til::size sz;
+        VERIFY_ARE_EQUAL(0, sz._width);
+        VERIFY_ARE_EQUAL(0, sz._height);
+    }
+
+    TEST_METHOD(RawConstruct)
+    {
+        const til::size sz{ 5, 10 };
+        VERIFY_ARE_EQUAL(5, sz._width);
+        VERIFY_ARE_EQUAL(10, sz._height);
+    }
+
+    TEST_METHOD(UnsignedConstruct)
+    {
+        Log::Comment(L"0.) Normal unsigned construct.");
+        {
+            const size_t width = 5;
+            const size_t height = 10;
+
+            const til::size sz{ width, height };
+            VERIFY_ARE_EQUAL(5, sz._width);
+            VERIFY_ARE_EQUAL(10, sz._height);
+        }
+
+        Log::Comment(L"1.) Unsigned construct overflow on width.");
+        {
+            constexpr size_t width = std::numeric_limits<size_t>().max();
+            const size_t height = 10;
+
+            auto fn = [&]() {
+                til::size sz{ width, height };
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+
+        Log::Comment(L"2.) Unsigned construct overflow on height.");
+        {
+            constexpr size_t height = std::numeric_limits<size_t>().max();
+            const size_t width = 10;
+
+            auto fn = [&]() {
+                til::size sz{ width, height };
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+    }
+
+    TEST_METHOD(SignedConstruct)
+    {
+        const ptrdiff_t width = -5;
+        const ptrdiff_t height = -10;
+
+        const til::size sz{ width, height };
+        VERIFY_ARE_EQUAL(width, sz._width);
+        VERIFY_ARE_EQUAL(height, sz._height);
+    }
+
+    TEST_METHOD(CoordConstruct)
+    {
+        COORD coord{ -5, 10 };
+
+        const til::size sz{ coord };
+        VERIFY_ARE_EQUAL(coord.X, sz._width);
+        VERIFY_ARE_EQUAL(coord.Y, sz._height);
+    }
+
+    TEST_METHOD(SizeConstruct)
+    {
+        SIZE size{ 5, -10 };
+
+        const til::size sz{ size };
+        VERIFY_ARE_EQUAL(size.cx, sz._width);
+        VERIFY_ARE_EQUAL(size.cy, sz._height);
+    }
+
+    TEST_METHOD(Equality)
+    {
+        Log::Comment(L"0.) Equal.");
+        {
+            const til::size s1{ 5, 10 };
+            const til::size s2{ 5, 10 };
+            VERIFY_IS_TRUE(s1 == s2);
+        }
+
+        Log::Comment(L"1.) Left Width changed.");
+        {
+            const til::size s1{ 4, 10 };
+            const til::size s2{ 5, 10 };
+            VERIFY_IS_FALSE(s1 == s2);
+        }
+
+        Log::Comment(L"2.) Right Width changed.");
+        {
+            const til::size s1{ 5, 10 };
+            const til::size s2{ 6, 10 };
+            VERIFY_IS_FALSE(s1 == s2);
+        }
+
+        Log::Comment(L"3.) Left Height changed.");
+        {
+            const til::size s1{ 5, 9 };
+            const til::size s2{ 5, 10 };
+            VERIFY_IS_FALSE(s1 == s2);
+        }
+
+        Log::Comment(L"4.) Right Height changed.");
+        {
+            const til::size s1{ 5, 10 };
+            const til::size s2{ 5, 11 };
+            VERIFY_IS_FALSE(s1 == s2);
+        }
+    }
+
+    TEST_METHOD(Inequality)
+    {
+        Log::Comment(L"0.) Equal.");
+        {
+            const til::size s1{ 5, 10 };
+            const til::size s2{ 5, 10 };
+            VERIFY_IS_FALSE(s1 != s2);
+        }
+
+        Log::Comment(L"1.) Left Width changed.");
+        {
+            const til::size s1{ 4, 10 };
+            const til::size s2{ 5, 10 };
+            VERIFY_IS_TRUE(s1 != s2);
+        }
+
+        Log::Comment(L"2.) Right Width changed.");
+        {
+            const til::size s1{ 5, 10 };
+            const til::size s2{ 6, 10 };
+            VERIFY_IS_TRUE(s1 != s2);
+        }
+
+        Log::Comment(L"3.) Left Height changed.");
+        {
+            const til::size s1{ 5, 9 };
+            const til::size s2{ 5, 10 };
+            VERIFY_IS_TRUE(s1 != s2);
+        }
+
+        Log::Comment(L"4.) Right Height changed.");
+        {
+            const til::size s1{ 5, 10 };
+            const til::size s2{ 5, 11 };
+            VERIFY_IS_TRUE(s1 != s2);
+        }
+    }
+
+    TEST_METHOD(Addition)
+    {
+        Log::Comment(L"0.) Addition of two things that should be in bounds.");
+        {
+            const til::size sz{ 5, 10 };
+            const til::size sz2{ 23, 47 };
+
+            const til::size expected{ sz.width() + sz2.width(), sz.height() + sz2.height() };
+
+            VERIFY_ARE_EQUAL(expected, sz + sz2);
+        }
+
+        Log::Comment(L"1.) Addition results in value that is too large (width).");
+        {
+            constexpr ptrdiff_t bigSize = std::numeric_limits<ptrdiff_t>().max();
+            const til::size sz{ bigSize, static_cast<ptrdiff_t>(0) };
+            const til::size sz2{ 1, 1 };
+
+            auto fn = [&]() {
+                sz + sz2;
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+
+        Log::Comment(L"2.) Addition results in value that is too large (height).");
+        {
+            constexpr ptrdiff_t bigSize = std::numeric_limits<ptrdiff_t>().max();
+            const til::size sz{ static_cast<ptrdiff_t>(0), bigSize };
+            const til::size sz2{ 1, 1 };
+
+            auto fn = [&]() {
+                sz + sz2;
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+    }
+
+    TEST_METHOD(Subtraction)
+    {
+        Log::Comment(L"0.) Subtraction of two things that should be in bounds.");
+        {
+            const til::size sz{ 5, 10 };
+            const til::size sz2{ 23, 47 };
+
+            const til::size expected{ sz.width() - sz2.width(), sz.height() - sz2.height() };
+
+            VERIFY_ARE_EQUAL(expected, sz - sz2);
+        }
+
+        Log::Comment(L"1.) Subtraction results in value that is too small (width).");
+        {
+            constexpr ptrdiff_t bigSize = std::numeric_limits<ptrdiff_t>().max();
+            const til::size sz{ bigSize, static_cast<ptrdiff_t>(0) };
+            const til::size sz2{ -2, -2 };
+
+            auto fn = [&]() {
+                sz2 - sz;
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+
+        Log::Comment(L"2.) Subtraction results in value that is too small (height).");
+        {
+            constexpr ptrdiff_t bigSize = std::numeric_limits<ptrdiff_t>().max();
+            const til::size sz{ static_cast<ptrdiff_t>(0), bigSize };
+            const til::size sz2{ -2, -2 };
+
+            auto fn = [&]() {
+                sz2 - sz;
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+    }
+
+    TEST_METHOD(Multiplication)
+    {
+        Log::Comment(L"0.) Multiplication of two things that should be in bounds.");
+        {
+            const til::size sz{ 5, 10 };
+            const til::size sz2{ 23, 47 };
+
+            const til::size expected{ sz.width() * sz2.width(), sz.height() * sz2.height() };
+
+            VERIFY_ARE_EQUAL(expected, sz * sz2);
+        }
+
+        Log::Comment(L"1.) Multiplication results in value that is too large (width).");
+        {
+            constexpr ptrdiff_t bigSize = std::numeric_limits<ptrdiff_t>().max();
+            const til::size sz{ bigSize, static_cast<ptrdiff_t>(0) };
+            const til::size sz2{ 10, 10 };
+
+            auto fn = [&]() {
+                sz* sz2;
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+
+        Log::Comment(L"2.) Multiplication results in value that is too large (height).");
+        {
+            constexpr ptrdiff_t bigSize = std::numeric_limits<ptrdiff_t>().max();
+            const til::size sz{ static_cast<ptrdiff_t>(0), bigSize };
+            const til::size sz2{ 10, 10 };
+
+            auto fn = [&]() {
+                sz* sz2;
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+    }
+
+    TEST_METHOD(Division)
+    {
+        Log::Comment(L"0.) Division of two things that should be in bounds.");
+        {
+            const til::size sz{ 555, 510 };
+            const til::size sz2{ 23, 47 };
+
+            const til::size expected{ sz.width() / sz2.width(), sz.height() / sz2.height() };
+
+            VERIFY_ARE_EQUAL(expected, sz / sz2);
+        }
+
+        Log::Comment(L"1.) Division by zero");
+        {
+            constexpr ptrdiff_t bigSize = std::numeric_limits<ptrdiff_t>().max();
+            const til::size sz{ bigSize, static_cast<ptrdiff_t>(0) };
+            const til::size sz2{ 1, 1 };
+
+            auto fn = [&]() {
+                sz2 / sz;
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+    }
+
+    TEST_METHOD(DivisionRoundingUp)
+    {
+        Log::Comment(L"1.) Division rounding up with positive result.");
+        {
+            const til::size sz{ 10, 5 };
+            const til::size divisor{ 3, 2 };
+
+            // 10 / 3 is 3.333, rounded up is 4.
+            // 5 / 2 is 2.5, rounded up is 3.
+            const til::size expected{ 4, 3 };
+
+            VERIFY_ARE_EQUAL(expected, sz.divide_ceil(divisor));
+        }
+
+        Log::Comment(L"2.) Division rounding larger(up) with negative result.");
+        {
+            const til::size sz{ -10, -5 };
+            const til::size divisor{ 3, 2 };
+
+            // -10 / 3 is -3.333, rounded up is -4.
+            // -5 / 2 is -2.5, rounded up is -3.
+            const til::size expected{ -4, -3 };
+
+            VERIFY_ARE_EQUAL(expected, sz.divide_ceil(divisor));
+        }
+    }
+
+    TEST_METHOD(Width)
+    {
+        const til::size sz{ 5, 10 };
+        VERIFY_ARE_EQUAL(sz._width, sz.width());
+    }
+
+    TEST_METHOD(WidthCast)
+    {
+        const til::size sz{ 5, 10 };
+        VERIFY_ARE_EQUAL(static_cast<SHORT>(sz._width), sz.width<SHORT>());
+    }
+
+    TEST_METHOD(Height)
+    {
+        const til::size sz{ 5, 10 };
+        VERIFY_ARE_EQUAL(sz._height, sz.height());
+    }
+
+    TEST_METHOD(HeightCast)
+    {
+        const til::size sz{ 5, 10 };
+        VERIFY_ARE_EQUAL(static_cast<SHORT>(sz._height), sz.height<SHORT>());
+    }
+
+    TEST_METHOD(Area)
+    {
+        Log::Comment(L"0.) Area of two things that should be in bounds.");
+        {
+            const til::size sz{ 5, 10 };
+            VERIFY_ARE_EQUAL(sz._width * sz._height, sz.area());
+        }
+
+        Log::Comment(L"1.) Area is out of bounds on multiplication.");
+        {
+            constexpr ptrdiff_t bigSize = std::numeric_limits<ptrdiff_t>().max();
+            const til::size sz{ bigSize, bigSize };
+
+            auto fn = [&]() {
+                sz.area();
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+    }
+
+    TEST_METHOD(CastToCoord)
+    {
+        Log::Comment(L"0.) Typical situation.");
+        {
+            const til::size sz{ 5, 10 };
+            COORD val = sz;
+            VERIFY_ARE_EQUAL(5, val.X);
+            VERIFY_ARE_EQUAL(10, val.Y);
+        }
+
+        Log::Comment(L"1.) Overflow on width.");
+        {
+            constexpr ptrdiff_t width = std::numeric_limits<ptrdiff_t>().max();
+            const ptrdiff_t height = 10;
+            const til::size sz{ width, height };
+
+            auto fn = [&]() {
+                COORD val = sz;
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+
+        Log::Comment(L"2.) Overflow on height.");
+        {
+            constexpr ptrdiff_t height = std::numeric_limits<ptrdiff_t>().max();
+            const ptrdiff_t width = 10;
+            const til::size sz{ width, height };
+
+            auto fn = [&]() {
+                COORD val = sz;
+            };
+
+            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+        }
+    }
+
+    TEST_METHOD(CastToSize)
+    {
+        Log::Comment(L"0.) Typical situation.");
+        {
+            const til::size sz{ 5, 10 };
+            SIZE val = sz;
+            VERIFY_ARE_EQUAL(5, val.cx);
+            VERIFY_ARE_EQUAL(10, val.cy);
+        }
+
+        Log::Comment(L"1.) Fit max width into SIZE (may overflow).");
+        {
+            constexpr ptrdiff_t width = std::numeric_limits<ptrdiff_t>().max();
+            const ptrdiff_t height = 10;
+            const til::size sz{ width, height };
+
+            // On some platforms, ptrdiff_t will fit inside cx/cy
+            const bool overflowExpected = width > std::numeric_limits<decltype(SIZE::cx)>().max();
+
+            if (overflowExpected)
+            {
+                auto fn = [&]() {
+                    SIZE val = sz;
+                };
+
+                VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+            }
+            else
+            {
+                SIZE val = sz;
+                VERIFY_ARE_EQUAL(width, val.cx);
+            }
+        }
+
+        Log::Comment(L"2.) Fit max height into SIZE (may overflow).");
+        {
+            constexpr ptrdiff_t height = std::numeric_limits<ptrdiff_t>().max();
+            const ptrdiff_t width = 10;
+            const til::size sz{ width, height };
+
+            // On some platforms, ptrdiff_t will fit inside cx/cy
+            const bool overflowExpected = height > std::numeric_limits<decltype(SIZE::cy)>().max();
+
+            if (overflowExpected)
+            {
+                auto fn = [&]() {
+                    SIZE val = sz;
+                };
+
+                VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_ABORT; });
+            }
+            else
+            {
+                SIZE val = sz;
+                VERIFY_ARE_EQUAL(height, val.cy);
+            }
+        }
+    }
+
+    TEST_METHOD(CastToD2D1SizeF)
+    {
+        Log::Comment(L"0.) Typical situation.");
+        {
+            const til::size sz{ 5, 10 };
+            D2D1_SIZE_F val = sz;
+            VERIFY_ARE_EQUAL(5, val.width);
+            VERIFY_ARE_EQUAL(10, val.height);
+        }
+
+        // All ptrdiff_ts fit into a float, so there's no exception tests.
+    }
+};
diff --git a/src/til/ut_til/SomeTests.cpp b/src/til/ut_til/SomeTests.cpp
index 981a726cd..e7a1c0258 100644
--- a/src/til/ut_til/SomeTests.cpp
+++ b/src/til/ut_til/SomeTests.cpp
@@ -2,7 +2,6 @@
 // Licensed under the MIT license.
 
 #include "precomp.h"
-#include "WexTestClass.h"
 
 using namespace WEX::Common;
 using namespace WEX::Logging;
diff --git a/src/til/ut_til/til.unit.tests.vcxproj b/src/til/ut_til/til.unit.tests.vcxproj
index bfa70c72f..750931c19 100644
--- a/src/til/ut_til/til.unit.tests.vcxproj
+++ b/src/til/ut_til/til.unit.tests.vcxproj
@@ -10,6 +10,7 @@
   </PropertyGroup>
   <Import Project="$(SolutionDir)src\common.build.pre.props" />
   <ItemGroup>
+    <ClCompile Include="SizeTests.cpp" />
     <ClCompile Include="ColorTests.cpp" />
     <ClCompile Include="SomeTests.cpp" />
     <ClCompile Include="..\precomp.cpp">
diff --git a/src/til/ut_til/til.unit.tests.vcxproj.filters b/src/til/ut_til/til.unit.tests.vcxproj.filters
new file mode 100644
index 000000000..c78750fac
--- /dev/null
+++ b/src/til/ut_til/til.unit.tests.vcxproj.filters
@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup>
+    <Natvis Include="$(SolutionDir)tools\ConsoleTypes.natvis" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClCompile Include="SomeTests.cpp" />
+    <ClCompile Include="..\precomp.cpp" />
+    <ClCompile Include="u8u16convertTests.cpp" />
+    <ClCompile Include="SizeTests.cpp" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClInclude Include="..\precomp.h" />
+  </ItemGroup>
+</Project>
\ No newline at end of file
diff --git a/tools/ConsoleTypes.natvis b/tools/ConsoleTypes.natvis
index 31340c96d..8d09a1a67 100644
--- a/tools/ConsoleTypes.natvis
+++ b/tools/ConsoleTypes.natvis
@@ -80,7 +80,11 @@
         <DisplayString Condition="_keyDown">{{↓  wch:{_charData} mod:{_activeModifierKeys} repeat:{_repeatCount} vk:{_virtualKeyCode} vsc:{_virtualScanCode}}</DisplayString>
         <DisplayString Condition="!_keyDown">{{↑ wch:{_charData} mod:{_activeModifierKeys} repeat:{_repeatCount} vk:{_virtualKeyCode} vsc:{_virtualScanCode}}</DisplayString>
     </Type>
-  
+
+    <Type Name="til::size">
+        <DisplayString>{{W: {_width,d} x H: {_height,d} -> A: {_width * _height, d}}}</DisplayString>
+    </Type>
+
     <Type Name="til::color">
       <DisplayString>{{RGB: {(int)r,d}, {(int)g,d}, {(int)b,d}; α: {(int)a,d}}}</DisplayString>
     </Type>