Calculate fov from your inputs, with a result breakdown and worked steps.
FOV Formula and Method
Horizontal FOV = 2 atan(tan(vertical FOV / 2) × width / height)
Use the actual rendered viewport width and height, or an equivalent aspect-ratio pair such as 16 and 9. Enter a full horizontal or vertical angle in degrees. The trigonometric conversion works with half angles because each half of the view forms a right triangle around the viewing axis.
How to Use This Calculator
Select the result and any applicable method before entering the visible values. Check the selected record, unit and scoring conventions before calculating. Review the primary result and its breakdown, then open the calculation steps to see how the inputs were used.
Worked Example
With the example inputs in the table, the result is 58.7155°. This converts rectilinear full-angle horizontal and vertical fields of view.
Vertical FOV = 2 atan(tan(horizontal FOV / 2) ÷ (width / height))
Input and Example Guide
| Input or category | Example or weight | Entry guidance |
|---|---|---|
| Known full field-of-view angle | Horizontal angle | Choose the convention that applies to your record. |
| Known full angle (degrees) | 90 | Use the stated unit; retain available precision. |
| Viewport width (pixels or ratio units) | 16 | Use the stated unit; retain available precision. |
| Viewport height (same unit) | 9 | Use the stated unit; retain available precision. |
Interpreting the Result
At a fixed vertical angle, increasing width relative to height increases the horizontal angle. A 90-degree horizontal angle at 16:9 corresponds to about 58.72 degrees vertically. Games that display a reference-aspect slider, crop the image, or use fisheye projection need their own convention before this geometric relationship applies.
Game settings can use horizontal, vertical, diagonal or reference-aspect conventions. Supply the actual full angle and aspect ratio; fisheye and game-specific crop rules are excluded.
Assumptions and Common Input Errors
This converts rectilinear full-angle horizontal and vertical fields of view. Use credited records rather than mixing estimates with final totals. A blank field is not treated as zero; enter zero explicitly when it is a valid observation.
Saving and Revising a Scenario
A successful calculation is saved in this browser and can be restored on the next visit. Editing an input clears the old result so it is not mistaken for an updated calculation. Reset returns the example inputs and clears the saved result.
Sources
Khronos Group, OpenGL perspective projection documentation, reviewed 2026.