Convert a field of view between horizontal and vertical measurement at 16:9, 16:10, 4:3, 21:9 or 32:9. Pure geometry, no game-specific constants.
| Input | Result |
|---|---|
| 90° vertical on 16:9 | 121.28° horizontal |
| 103° vertical on 16:9 | 131.79° horizontal |
| 90° vertical on 4:3 | 106.26° horizontal |
| 103° vertical on 16:10 | 127.13° horizontal |
| 106° vertical on 21:9 | 144.2° horizontal |
| 106° horizontal on 16:9 | 73.48° vertical |
| 121° horizontal on 16:9 | 89.67° vertical |
A field-of-view number is meaningless until you know whether it is measured horizontally or vertically, and games do not agree on which one they put in the settings menu. On the same 16:9 monitor, 90 vertical becomes about 121 horizontal, the same view, described by a number 31 degrees larger.
The conversion is pure geometry, with no game-specific constant involved:
hFOV = 2 · atan( tan(vFOV / 2) × aspect )
vFOV = 2 · atan( tan(hFOV / 2) ÷ aspect )
where aspect is width ÷ height: 16:9 is 1.778, 16:10 is 1.6, 4:3 is 1.333, 21:9 is 2.333, 32:9 is 3.556. Note what this means for anyone comparing monitors: switching from 16:9 to 21:9 while holding the vertical FOV fixed widens the horizontal view substantially, which is why ultrawide players often see more than they expect at the same settings number.
This page converts the number. It does not tell you which measurement your particular game uses in its options screen, that differs per title and changes between versions, so check the game itself before typing anything in.
That depends entirely on the game, which is the problem this page exists to solve. Enter the number and your aspect ratio and it will tell you what the other measurement is; check which one your game actually uses before copying a setting.
Because horizontal distance across a 16:9 screen is 1.778× the vertical, and the tangent in the formula is not linear, the wider the starting angle, the bigger the gap.
It changes what the same settings number means. Holding vertical FOV fixed on a wider aspect ratio widens the horizontal view, which is why 21:9 players see noticeably more at the same setting.
It is a trade-off. A wider view shows more around you but shrinks distant targets and costs performance. It is a preference, not a number to optimise.