FOV Calculator

Field of View (FOV) is the angular extent of the game world visible on screen at any given moment. It is measured in degrees and determines how much of your surroundings you can see without moving the camera. A higher FOV shows more of the environment but can introduce perspective distortion near screen edges, while a lower FOV produces a narrower, more zoomed-in view that feels cinematic but limits peripheral awareness.

In competitive gaming, FOV is one of the most consequential settings on your list. Spotting flanking enemies in a battle royale, tracking fast-moving targets in a first-person shooter, or navigating dense environments in a third-person action game all depend on how wide your field of view is set. Professional players and content creators spend significant time optimizing this single value because it directly affects reaction time, situational awareness, and even motion sickness at extreme values.

FOV can be expressed in three ways depending on which axis is used as the reference:

• Horizontal FOV (hFOV) — the angle from left screen edge to right screen edge. This is the most common form reported in game settings menus.
• Vertical FOV (vFOV) — the angle from the top edge to the bottom edge of the screen. Some engines, such as idTech and older Source-based games, expose only vFOV in console commands.
• Diagonal FOV (dFOV) — the angle measured corner to corner across the full screen. Less common but occasionally referenced in technical documentation.

Because the three values are tightly coupled through the aspect ratio of your display, knowing any one of them lets you derive the other two — which is precisely what this FOV calculator does.

The relationship between horizontal, vertical, and diagonal FOV is governed by basic trigonometry. All three formulas use the half-angle tangent identity along with the display's aspect ratio. The aspect ratio is simply the width divided by the height of the screen resolution or the selected ratio preset (e.g., 16:9, 21:9, 4:3).

For a given horizontal FOV and aspect ratio W:H, the vertical FOV is derived by dividing the tangent of the half-angle by the aspect ratio before taking the arctangent. Going the other direction — from vertical to horizontal — the tangent of the half-angle is multiplied by the aspect ratio. Diagonal FOV uses a modified ratio that incorporates the full diagonal length relative to either the horizontal or vertical axis.

The zoom factor computed alongside the conversion compares your effective magnification relative to a reference 90° horizontal FOV, using the same half-angle tangent approach:

Zoom = tan(90° / 2) / tan(hFOV / 2)

A zoom factor greater than 1.0 means the view is more magnified than 90° hFOV; less than 1.0 means a wider, less magnified view.

When you switch from a 16:9 monitor to an ultrawide 21:9 panel — or any non-standard aspect ratio — the question is: which FOV value should you enter in the game to preserve the same vertical view you had before? The answer is Hor+ (Horizontal Plus) scaling, the industry-standard method used by most modern titles.

Hor+ scaling keeps the vertical FOV fixed and adds more image to the left and right. It is the fairest method for widescreen players because it does not crop any of the original view; it simply reveals more. The alternative, Vert- (Vertical Minus) scaling, would crop the top and bottom to fit the wider canvas, punishing ultrawide users — and it is rarely used in modern games.

The Hor+ calculation in this FOV calculator works as follows:

1. Take the base horizontal FOV you had at 16:9.
2. Derive the preserved vertical FOV: vFOV = 2 × atan(tan(hFOV/2) / (16/9))
3. Compute the new horizontal FOV for the target aspect ratio: newHFOV = 2 × atan(tan(vFOV/2) × (newW / newH))

For example, if you play at 90° on 16:9, the equivalent Hor+ setting for 21:9 is approximately 106.26°, and for 32:9 it is approximately 134.79°. These are the values you should enter in your game's FOV slider when moving to an ultrawide or super-ultrawide monitor.

Understanding Hor+ scaling is especially important for competitive players, where ultrawide displays are increasingly common. Entering an arbitrary high FOV instead of the Hor+-correct value can inadvertently change the vertical perspective, affecting muscle memory and aim.

Not all games use the same FOV axis as their primary setting. Understanding which axis a particular engine or game exposes helps you translate values correctly when using an external FOV calculator.

Whenever you encounter a game that exposes vertical FOV, enter that value into this calculator with the Vertical source type to instantly get the equivalent horizontal reading, making it easy to compare against other titles or to verify your settings against your preferred angle.

Selecting the right FOV is a balance between situational awareness and target visibility. Higher FOV values give you a wider picture of the battlefield — you can see flankers earlier and react faster to multiple threats. However, enemies appear smaller on screen at higher FOV settings, which can make aiming more difficult, particularly at long range. Lower FOV values bring distant targets closer but limit peripheral vision and can increase the risk of being caught off-guard.

Most competitive first-person shooter players settle in the 90°–110° horizontal FOV range. Values around 90°–100° are the traditional sweet spot for CS-style tactical shooters where long-range precision matters. Players who prioritize movement-heavy games like Apex Legends or Call of Duty often prefer 100°–110° for the wider situational view those games reward.

Another factor is motion sickness. Some players experience nausea or disorientation at very high FOV values (above 120° horizontal), especially on close-distance monitors. If you are sensitive to this, start at 90° and increase gradually, pausing to assess comfort at each step.

Frame rate also plays a role. Wider FOV requires the engine to render more geometry per frame, which can reduce frames per second on less powerful systems. If you are already GPU-limited, a modest FOV reduction may improve smoothness more than any graphical setting change.

Finally, consider your monitor size and viewing distance. A 27-inch 4K display viewed from 60 cm fills more of your real-world visual field than a 24-inch 1080p screen at the same distance, so a slightly lower in-game FOV may feel equally expansive. Use this FOV calculator as a starting point, then tune in small 5° increments until the balance of awareness and precision feels natural for your setup and playstyle.