Real Geometry, Not a Guess
Field of View & Lens Distortion Calculator
No browser can read a camera's field of view directly — it has to be calculated from real-world geometry, using an object of known width at a known distance as an anchor. Hold up a ruler, a sheet of paper, or a credit card, drag the two guide lines to match its edges, enter its real width and distance, and get your camera's exact horizontal, vertical, and diagonal FOV in degrees.
Step 1
Align the Guide Lines
Hold your reference object flat, facing the camera, at the distance you will enter below. Drag the two lines so they line up with its left and right edges.
Step 2
Enter Real-World Measurements
Result
Field of View
Optional
Lens Distortion Self-Check
Frame a known straight line — a door frame, wall corner, or bookshelf edge — so it runs from one side of the view to the other. Toggle the grid, and compare the real edge against the straight overlay line.
Does the real-world straight edge bow away from the grid line toward the frame's edges?
Notes
Where these numbers come from
Given an object of known width filling a known fraction of the frame at a known distance, horizontal field of view follows directly from trigonometry: 2 × atan( width / (2 × fraction × distance) ). Vertical and diagonal FOV are derived from that using your camera's actual pixel aspect ratio and standard rectilinear-lens geometry. Given accurate inputs, this is an exact calculation, not an estimate — the only source of error is how precisely you measure distance and align the guide lines.
Typical FOV by camera type
| Diagonal FOV | Camera type | What to expect |
|---|---|---|
| 60 – 70° | Older/budget laptop cameras | Narrower, portrait-style framing. |
| 78 – 90° | Common single-person webcams | Room to move without excessive background. |
| 110 – 120°+ | Conference-room / wide-angle cameras | Fits several people; more visible barrel distortion at edges. |
Step-by-Step
How to Measure Your FOV
- Click "Start" and allow camera access when prompted.
- Place an object of known width — a ruler, credit card, or sheet of paper — at a measured distance from the lens.
- Drag the guide lines to align exactly with the object's edges in frame.
- Enter the real width and distance to get your calculated horizontal, vertical, and diagonal FOV.
Common Questions