This FOV calculator converts your field of view between games and between monitor aspect ratios using the same Horizontal-Plus (Hor+) math that drives most modern shooters. Type a value, tell it whether the number is a horizontal or vertical FOV, pick your aspect ratios, and it returns the equivalent horizontal and vertical angles. Everything runs locally in your browser — no data leaves your machine.
90 horizontal at 4:3 expands to 106.26° horizontal on a 16:9 monitor, while the vertical FOV stays fixed at 73.74°. If your calculator returns those exact figures for 90 (4:3 horizontal) → 16:9, it is doing the trigonometry correctly.FOV is an angle, so the conversion is pure trigonometry rather than a simple ratio. The on-screen image is a flat plane at a fixed distance, and the horizontal and vertical viewing angles are tied together by the screen's width-to-height ratio. The two relationships you need are:
Vdeg = 2 × atan( tan(Hdeg / 2) / (width / height) )Hdeg = 2 × atan( tan(Vdeg / 2) × (width / height) )For converting a horizontal FOV defined at one aspect ratio into the horizontal FOV at another aspect ratio (the heart of "4:3 to 16:9"), Hor+ games keep vertical FOV constant, which reduces to:
newH = 2 × atan( tan(oldH / 2) × (newAspect / oldAspect) )Because the tangent function is non-linear, you cannot just multiply your FOV by 16/9 over 4/3. A naive multiply gives 120° for CS's 90; the correct trigonometric answer is 106.26°. That gap is exactly why a dedicated calculator is worth using.
Three scaling philosophies exist, and they change what happens when you go wide:
| Scaling | What stays fixed | Going from 4:3 to 16:9 | Typical games |
|---|---|---|---|
| Hor+ (Horizontal Plus) | Vertical FOV | You see more to the sides | CS2, Apex, most modern FPS |
| Vert- (Vertical Minus) | Horizontal FOV | You see less on top/bottom | Some older console ports |
| Stretched / anamorphic | Nothing (image distorts) | Models look wider; no true FOV gain | CS pros on 4:3 stretched |
The vast majority of competitive PC shooters are Hor+, which is the model this calculator uses by default. That is also the reason ultrawide users genuinely see opponents peeking from the sides a fraction earlier — it is not placebo, it is geometry. Note that some titles, including Valorant and certain ranked CS configurations, lock or restrict aspect-ratio FOV gains specifically to neutralise that advantage.
Use these as sensible starting points, then tune by feel. Values are expressed in the unit each game's settings menu uses. Where a game uses a 4:3-based horizontal slider (Source-engine lineage), that is noted.
| Game | FOV unit in menu | Default | Common competitive range |
|---|---|---|---|
| Counter-Strike 2 | Fixed 90 horizontal (4:3); not user-adjustable | 90 (4:3 H) | Locked — 4:3 stretched is a display choice, not an FOV change |
| Valorant | Effectively fixed (~71 vertical) | Fixed | Not adjustable |
| Apex Legends | Horizontal (4:3 base) | 90 | 104–110 |
| Overwatch 2 | Vertical | 103 | 103 (max) |
| Call of Duty (MW/Warzone) | Horizontal | 80 | 105–120 |
| Fortnite | No FOV slider (fixed ~80 H) | ~80 H | Locked |
| Quake Champions | Vertical | 110 | 110–130 |
If your favourite game locks FOV, you can still mirror the feel inside an aim trainer by converting the game's fixed FOV into your trainer's unit with the tool above. For example, to match Valorant's roughly 71° vertical FOV in a trainer that asks for horizontal FOV on a 16:9 screen, the calculator returns about 103° horizontal.
Aim is a calibrated motor skill: your brain learns how far a given mouse movement rotates the view, in degrees, for a fixed FOV. Change the FOV and every flick now covers a different number of on-screen pixels per degree, so the muscle memory you built partially resets. The deliberate-practice literature (Ericsson, Krampe & Tesch-Römer, 1993) stresses that consistent task conditions are a precondition for skill consolidation — FOV is one of those conditions, alongside sensitivity, DPI, and crosshair.
Practical rule: set your aim trainer to the converted equivalent of your main game's FOV, then leave both untouched for at least a few weeks before judging progress. If you switch games frequently, prioritise matching FOV (and effective sensitivity via cm/360) for whichever title you compete in most. For the sensitivity side of that equation, use our sensitivity converter and cm/360 calculator.
You play with the standard 90 horizontal FOV (4:3 reference) and buy a 3440x1440 (21:9, ratio 2.37) monitor. Feeding 90, "Horizontal (4:3 base)", target 21:9 returns about 121.28° horizontal — a substantial widening. In Hor+ titles that means more peripheral coverage; in FOV-locked titles the game will clamp it back.
Overwatch 2 caps FOV at 103, measured vertically. To replicate that in a trainer that wants horizontal FOV on 16:9, select "Vertical", value 103, target 16:9: the calculator returns roughly 131.8° horizontal, confirming OW2 runs an unusually wide view compared with CS.
Horizontal FOV measures the angle you can see left-to-right; vertical FOV measures top-to-bottom. They are linked by your aspect ratio: Vdeg = 2 × atan( tan(Hdeg/2) / (width/height) ). On a 16:9 monitor a 106.26° horizontal FOV equals a 73.74° vertical FOV.
Most competitive shooters use Hor+ scaling, which keeps vertical FOV constant and widens horizontal FOV as the screen gets wider. The formula is newH = 2 × atan( tan(oldH/2) × newAspect/oldAspect ). A CS2-style 90° horizontal FOV defined at 4:3 becomes 106.26° on a 16:9 display.
Hor+ is the most common FOV scaling method in modern FPS games. It holds your vertical field of view fixed and adds more horizontal view as the aspect ratio widens. A wider monitor literally lets you see more to the sides, which is why ultrawide players get a competitive sight advantage in Hor+ games.
Match your aim trainer FOV to the game you play most. For CS2 train near 90 (4:3 horizontal). For Valorant the effective vertical FOV is fixed, so set your trainer to roughly 71 vertical. For Apex Legends 104–110 (4:3 horizontal) is common. Consistent FOV preserves the muscle memory you build between trainer and game.
Higher FOV shows more of the screen but makes distant targets smaller, so flicks cover more angular distance per pixel. Lower FOV zooms targets in and can improve long-range tap accuracy at the cost of peripheral awareness. There is no universally best value; pick one, keep it constant, and let your muscle memory adapt.