Crop Factor Calculator

Sensor

Focal length, mm

Aperture f/

Your own crop factor

Leave at 0 to use the list.

Result

Equivalent focal length, mm52.5
Equivalent aperture f/2.7
Crop factor1.5
Full-frame focal for the same view, mm23.3
Times less light collected2.25
SensorAPS-C 23.5×15.6

One number, two different meanings

Converts focal length and aperture into full-frame equivalents for APS-C, Micro Four Thirds and other sensor sizes.

Crop factor is how many times smaller your sensor's diagonal is than full frame. Multiply focal length by it and you get the lens that would give the same field of view on full frame: 35 mm on APS-C behaves like 52.5 mm.

Aperture is still argued over. Exposure does not care about crop factor — f/1.8 is f/1.8 to the meter. But depth of field and total light gathered do care: on those two counts, f/1.8 on APS-C behaves like f/2.7 on full frame.

What this calculator shows

The equivalent focal length by field of view
The equivalent aperture by depth of field and light gathered
The full-frame focal length that would give the same frame

What to keep in mind

Equivalent aperture applies to depth of field and light-collecting area, not to exposure: a light meter never sees it.
Canon's APS-C crop factor is 1.6 and everyone else's is 1.5 — a small difference, but it shows in the result.

FAQs

What is crop factor?

The ratio of the full-frame diagonal to your sensor's. APS-C is 1.5 to 1.6, Micro Four Thirds is 2.0, a one-inch sensor is 2.7.

What is 35 mm on a crop body?

52.5 mm of field of view at a crop factor of 1.5, or 56 mm at 1.6. Roughly the classic fifty.

Does crop factor change the light gathered?

For exposure, no: f/1.8 stays f/1.8 with the same shutter and ISO. For depth of field and total light on the sensor, yes — multiply the aperture by the crop factor.

Why bother with equivalents?

To compare gear across formats. Without the conversion there is no telling whether a 25 mm on Micro Four Thirds gives the same frame as a 50 mm on full frame.

Worked example

A fast thirty-five on a crop body

Input: APS-C 1.5, a 35 mm f/1.8 lens

Output: 52.5 mm and f/2.7 in full-frame terms

Note: Which is exactly why 35 mm is the standard lens on a crop body: its field of view matches the classic fifty. It blurs backgrounds like an f/2.7, though, not an f/1.8.

Useful links

All tools in Photo & Video

Crop Factor Calculator

Result

Related tools

Depth of Field Calculator

Exposure Calculator

Screen PPI Calculator

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