Field of View Calculator
A lens does not change when you put it on a different camera. It projects the same image circle either way; a smaller sensor simply captures less of it, which crops the view rather than magnifying it. That distinction matters because the crop factor tells you the framing equivalence and nothing else — depth of field does not follow the same rule, which is why smaller sensors give more of it at the same framing.
What this generator does
Works out the angle of view across, down and diagonally from the focal length and the sensor's physical dimensions, and derives the crop factor from the ratio of sensor diagonals against full frame.
How to use this tool
- Enter a focal length and choose a sensor size.
- Read the horizontal, vertical and diagonal angles.
- Compare the full-frame equivalent against the actual focal length.
- Switch sensors with the same lens and watch the view crop rather than zoom.
Understanding the controls
- Focal length
- Between 8 and 800 mm — the actual focal length engraved on the lens, not an equivalent.
- Sensor
- Full frame, APS-C, Micro Four Thirds, one inch or medium format. The physical dimensions are what determine the view; the megapixel count is irrelevant to it.
Common use cases
- Working out what a lens will see before buying it
- Translating a focal length between camera systems
- Choosing a lens for a specific framing from a known distance
- Understanding what crop factor does and does not mean
- Comparing sensor formats on the same lens
How this generator works
The angle across a sensor dimension is twice the arctangent of half that dimension over the focal length — straightforward trigonometry on the triangle from the lens to the sensor edges. The check verifies all three angles independently and confirms they are correctly ordered: the diagonal must be the widest and the vertical the narrowest, which follows from the sensor being wider than it is tall.
Randomness and fairness
Nothing here is random. The field of view follows entirely from the focal length and sensor size you choose.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- Sensor dimensions are nominal. Individual cameras vary slightly, particularly APS-C, where Canon's is smaller than everyone else's.
- Assumes a rectilinear lens. Fisheye lenses project differently and cover far more than this arithmetic suggests.
- Field of view equivalence is about framing only. Depth of field and perspective do not follow the crop factor.
- Focus breathing changes a lens's effective focal length as it focuses closer.
Privacy and your data
The trigonometry runs in your browser. The lens and sensor you choose are never transmitted or stored.
Related generators
- Depth of Field CalculatorWhere the sharp zone starts and ends, with the hyperfocal distance and the identity that makes it special.
- Equivalent Exposure CalculatorEvery combination of aperture, shutter and ISO that gives the same brightness, matched on exposure value rather than guessed.
- Print Resolution CalculatorHow large an image prints at a given resolution, in inches and centimetres, with an honest verdict on quality.
- Crop Ratio CalculatorThe largest crop of a chosen ratio that an image can give, in exact whole multiples, with the offset to centre it and the area you keep.