FOV ↔ Focal Length Calculator
Convert between field of view and focal length for cameras, game engines and lenses, for any sensor/film size.
Game engines specify cameras by vertical FOV; photographers by focal length on a sensor. A 50mm lens on full-frame (36mm) gives ~40° horizontal — the 'normal' near-human perspective. Wider sensors or shorter focal = wider FOV. Crop sensors multiply the effective focal length.
Formula
About FOV ↔ Focal Length Calculator
Photographers think in millimeters of focal length; game and 3D engines think in degrees of field of view — and converting between them requires knowing the sensor or film size, because the same lens gives a different FOV on different sensors. This calculator does both directions for any sensor width, using the exact projection geometry (FOV = 2·atan(sensor / 2·focal)). It's essential for matching a virtual camera to a real one, choosing a lens for a target framing, understanding crop factor, or setting an engine camera that feels natural rather than fish-eyed or telephoto-flat.
How to use FOV ↔ Focal Length Calculator
- 1Enter your values into FOV ↔ Focal Length Calculator — sensible, domain-typical defaults are pre-filled so you see a real result immediately.
- 2The result recomputes live using the formula shown on the page; there is no button to press.
- 3Adjust any input to compare scenarios, then read the worked example to see the substituted numbers.
Why use FOV ↔ Focal Length Calculator?
- ✓Computes FOV ↔ Focal Length instantly in your browser — no sign-up, no upload, no server round-trip.
- ✓100% free and unlimited, with the exact formula shown: FOV = 2.
- ✓Runs entirely client-side, so every value you enter stays private on your device.
- ✓Live recompute as you type, with a worked example and authoritative references for trust.
Frequently asked questions
Why does focal length alone not determine FOV?+
FOV depends on the ratio of sensor size to focal length. A 50mm lens gives a ~40° horizontal view on full-frame (36mm wide) but a much narrower view on a smaller crop sensor, because less of the projected image circle is captured. That's the 'crop factor' — always specify sensor size when converting, which is exactly why this tool requires it.
Why do game engines use FOV instead of focal length?+
Because a virtual camera has no physical sensor — FOV directly defines how much of the scene the frustum captures, independent of any film format. Engines typically use VERTICAL FOV (Unity, Unreal) so aspect-ratio changes widen/narrow the view sensibly. Photographers use focal length because it's the physical, sensor-agnostic property of a real lens.
What's a natural-looking FOV?+
Roughly 40–60° horizontal approximates human central vision and looks natural — equivalent to a ~35–50mm lens on full-frame. Wider (90°+) introduces fish-eye distortion and is common in first-person games for peripheral awareness; narrower (telephoto) flattens perspective. Mismatched FOV is a frequent cause of motion sickness in VR and 'off'-feeling game cameras.
How do horizontal and vertical FOV relate?+
Through the aspect ratio. For a given focal length, horizontal FOV is wider than vertical on a landscape frame. Engines usually let you set one and derive the other from the viewport aspect. This tool reports horizontal FOV from sensor WIDTH and an estimated vertical for a 3:2 frame; for exact vertical, substitute the sensor height.
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