FOV Converter (horizontal ⇄ vertical, aspect ratio)

Understanding the FOV converter — concept and principle

Field of view (FOV) is how wide an angle of the game world you see on screen. Games describe it in different ways: some set a horizontal FOV, some a vertical one, and the same horizontal number gives a different picture on a 16:9, 21:9 or 4:3 screen. This converter turns a horizontal FOV into the vertical FOV, shows what the horizontal FOV becomes on a wider screen, and gives the equivalent 4:3 value that some games use for their FOV setting.

Hor+ scaling keeps the vertical angle and widens the horizontal one with the screen: 90° at 16:9 becomes 105.4° at 21:9.

How it is calculated

Vertical FOV = 2 × atan( tan(horizontal FOV ÷ 2) × height ÷ width ).
Horizontal FOV at a new aspect = 2 × atan( tan(vertical FOV ÷ 2) × new width ÷ height ).
Hor+ 4:3 equivalent = 2 × atan( tan(vertical FOV ÷ 2) × 4 ÷ 3 ).

Angles are in degrees. The aspect ratio is entered as width and height, for example 16 and 9.

The principle

Picture the camera at the tip of a pyramid looking at a flat screen. Half of the screen's width and the distance to the screen form a right triangle, so tan(half horizontal FOV) = half width ÷ distance, and the same holds for height. Because the distance is shared, the tangents of the half-angles are in the same ratio as width to height. FOV angles themselves are not proportional, which is why you cannot simply multiply 90° by 9/16. Most modern games use "Hor+" scaling: the vertical FOV stays fixed and a wider monitor shows extra picture at the sides.

Worked example

Defaults: horizontal FOV 90° at 16:9, new aspect 21:9.

tan(45°) = 1, so tan(vertical/2) = 1 × 9 ÷ 16 = 0.5625.
Vertical FOV = 2 × atan(0.5625) = 58.72°.
At 21:9: 2 × atan(0.5625 × 21 ÷ 9) = 2 × atan(1.3125) = 105.39°.
4:3 equivalent: 2 × atan(0.5625 × 4 ÷ 3) = 2 × atan(0.75) = 73.74°.

Each point is the calculator re-run with only “Horizontal FOV (°)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Horizontal FOV (°)	Vertical FOV (°)
22.5	12.7683386
45	26.23128755
67.5	41.1975094
90	58.71550709
112	80.18407759
135	107.2656486
180	180

How to read the result

A wider FOV shows more of the scene and makes motion feel faster, but targets look smaller. A narrower FOV magnifies the centre. If two games feel different with the "same" FOV, check whether one uses horizontal and the other vertical, and at which aspect ratio. As an example, CS2's fixed 90° at 4:3 is about 106.26° horizontal on a 16:9 screen, with the same 73.74° vertical FOV.

Common mistakes

Scaling FOV linearly with aspect ratio instead of using tangents.
Mixing up horizontal and vertical FOV settings between games.
Forgetting that some games define FOV at 4:3 regardless of your screen.
Swapping width and height when entering a resolution such as 2560 × 1080.

Keep in mind: Games may cap FOV, use different scaling methods or change them in updates. Use the result as a guide and check it in game.

Frequently asked questions

What FOV should I use?

It depends on screen size and viewing distance. Competitive players often prefer a wide FOV for awareness, while a narrower one can make distant targets easier to see. Try values within the game's range and keep the one you aim best with.

What is Vert− scaling?

Keeping horizontal FOV fixed and cutting the top and bottom on wider screens. It is the opposite of Hor+ and less common today.

Does FOV affect mouse sensitivity?

The cm/360 stays the same, but small aim adjustments look different because objects change size on screen.

Sources: Standard perspective projection geometry (pinhole camera model)

Checked 8 Nov 2026. Official league / federation formulas where they exist; widely used community formulas otherwise. For fun and analysis — not betting advice.

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