Camera Field of View Calculator
Find horizontal, vertical, and diagonal field of view plus frame size at a subject distance.
What it does
Field of view describes how much of a scene a lens captures. It is an angle, usually given in degrees, and it comes from two numbers: the size of the sensor and the focal length of the lens. A 50 mm lens on a full frame camera sees a narrower slice of the world than a 24 mm lens on the same body.
The same angle can describe a horizontal, vertical, or diagonal measurement. Horizontal field of view uses the sensor width, vertical uses the sensor height, and diagonal uses the distance from one corner to the other. Lens makers often quote the diagonal figure because it is the largest and looks impressive, but a photographer framing a landscape or a group portrait usually cares about the horizontal and vertical angles.
This calculator also reports the frame size at a chosen distance. That is the width and height of the area a lens will cover at the subject plane. It is useful for planning a group shot, checking whether a product fits in the frame, or working out how far back a camera must sit in a room.
The math assumes a rectilinear lens with no distortion and a flat subject plane. Wide lenses that rely on strong correction can bend straight lines near the edges, and fisheye lenses do not follow this model at all. For ordinary primes and zooms, the result is close enough for planning.
Angle of view changes when a lens made for one sensor size is mounted on another through an adapter. The calculator uses the sensor size you select, so choose the sensor that is actually behind the lens, not the one the lens was designed for.
How to use
- Pick metric or imperial for the subject distance.
- Select the sensor size that matches the camera body.
- Enter the lens focal length in millimeters.
- Enter the distance from the camera to the subject.
- Read the horizontal, vertical, and diagonal angles.
- Check the frame size to see how much of the subject fits.
Formula
- w
- Sensor width in millimeters.
- h
- Sensor height in millimeters.
- f
- Lens focal length in millimeters.
- d
- Distance from camera to subject in meters or feet.
- FOV
- Angle of view in degrees.
The angles do not change with distance. Only the frame size does. Frame width and height scale linearly with distance, so doubling the distance doubles the covered area at the subject. The diagonal of the sensor is sqrt(width^2 + height^2).
Worked example
Example: 50 mm lens on full frame at 5 m
Metric defaults: full frame sensor, 50 mm focal length, 5 m to the subject. The imperial mirror is 16.4 ft.
- Sensor width is 36 mm and height is 24 mm. The diagonal is sqrt(36^2 + 24^2) = 43.27 mm.
- Horizontal angle: 2 x atan(36 / (2 x 50)) = 2 x atan(0.36) = 39.6 degrees.
- Vertical angle: 2 x atan(24 / 100) = 2 x atan(0.24) = 27.0 degrees.
- Diagonal angle: 2 x atan(43.27 / 100) = 2 x atan(0.4327) = 46.8 degrees.
- Frame width: 5 x 36 / 50 = 3.60 m. Frame height: 5 x 24 / 50 = 2.40 m.
- The tool shows 39.6, 27.0, and 46.8 degrees and a frame of 3.60 m x 2.40 m.
- In imperial mode the same setup at 16.4 ft gives a frame of 11.81 ft x 7.87 ft.
Reference table
| Focal length | Horizontal FOV | Frame width at 5 m |
|---|---|---|
| 24 mm | 73.7° | 7.50 m |
| 35 mm | 54.4° | 5.14 m |
| 50 mm | 39.6° | 3.60 m |
| 85 mm | 23.9° | 2.12 m |
| 135 mm | 15.2° | 1.33 m |
Limits
- The formulas describe a rectilinear lens. Fisheye lenses and heavily corrected wide lenses do not follow them near the edges.
- Focus breathing can change the effective focal length at close distances, so macro work may differ from the calculated angle.
- The model assumes a flat subject plane perpendicular to the lens axis. A tilted camera or a curved subject changes the covered area.
- Sensor specifications are nominal. Actual active area can differ by a few tenths of a millimeter between camera models.
Common mistakes
- Using the lens mount's designed format instead of the sensor actually in the camera.
- Confusing diagonal field of view with horizontal field of view when comparing lenses.
- Entering distance in feet while the calculator is set to meters.
- Forgetting that frame size scales with distance, so a group that fits at 3 m will not fit at 2 m.
- Assuming a zoom lens holds exactly its marked focal length at every focus distance.
Try it yourself
Quick checks. Answers sit tucked under each question.
What is the horizontal field of view for a 24 mm lens on full frame at 10 m, and how wide is the frame?
73.7° horizontal, with a frame of 15.00 m x 10.00 m.
A 35 mm lens sits on an APS-C Canon body (22.3 x 14.9 mm) at 5 m. What is the horizontal angle and frame?
35.3° horizontal, with a frame of 3.19 m x 2.13 m.
A 50 mm lens on full frame focuses at 16.4 ft. What frame does it cover?
11.81 ft x 7.87 ft, with the same 39.6° horizontal angle as the metric case.
Questions
Does field of view change with distance?
No. The angle stays the same for a given sensor and focal length. The area covered at the subject grows with distance, but the angle does not.
Why is my lens advertised as 84 degrees when this shows less?
Lens ads usually quote the diagonal angle, and some quote it for a different sensor size. Check whether the figure is horizontal, vertical, or diagonal and which format it assumes.
What is crop factor?
Crop factor compares a sensor diagonal with full frame. A smaller sensor crops the image circle, so the same lens gives a narrower field of view.
Does focal length change when I focus closer?
Many lenses breathe, meaning the effective focal length shifts at close focus. The effect is small at normal distances and larger in macro work.
How do I calculate the diagonal angle?
Use the sensor diagonal in place of the width in the same formula. For full frame the diagonal is about 43.27 mm.
Can I use this for a phone camera?
Yes, if you know the sensor dimensions and the actual focal length in millimeters. Phone specs often list an equivalent focal length instead, which is not the same number.
Sources
- Edmund Optics, Understanding focal length and field of view
- MIT CSAIL, Lens and image formation fundamentals