FOV converter
Changing monitor or resolution changes what your FOV number means. This keeps your vertical view identical so the world looks the same size, just wider or narrower.
Why the number has to change
Most shooters set FOV horizontally, but what your eyes calibrate to is the vertical view — how big a player model looks at a given distance. Switch from 16:9 to 21:9 without adjusting and the game keeps your horizontal number, which forces the vertical view to shrink: everything looks zoomed in and your aim calibration quietly breaks.
The fix is Hor+ thinking: hold vertical FOV constant and recompute the horizontal number for the new aspect. That's exactly what this does — it converts your horizontal FOV to vertical, keeps that fixed, then converts back at the target aspect. Your world stays the same scale; you simply see more or less to the sides.
Common cases: 16:9 to 21:9 raises the horizontal number substantially, 16:9 to 4:3 lowers it (which is why stretched-res CS players run lower FOV numbers than they expect), and any 16:9 resolution to another 16:9 resolution needs no change at all — aspect is what matters, not pixel count.
Questions
Does my game use horizontal or vertical FOV?
Most first-person shooters use horizontal, which is what this assumes. Some engines and many racing and flight sims use vertical. If your game's FOV slider tops out around 90, it's likely vertical; if it goes past 100, it's almost certainly horizontal.
What's Hor+ and does it matter here?
Hor+ means the game adds horizontal view on wider screens while keeping vertical fixed — the good behavior, and what this calculator assumes. Older Vert− games shrink your vertical view instead, which is why some old titles feel zoomed in on ultrawide no matter what you set.
Should I just max my FOV?
Higher FOV shows more but shrinks distant targets, making precise long-range aim harder. Most competitive players land somewhere in the middle rather than at either extreme — and whatever you pick, keep it stable, since FOV changes recalibrate your aim just like sensitivity changes do.