Photography
Crop factor and equivalence.
Choose a sensor and enter the lens. See the crop factor, the full-frame equivalent focal length and f-number, and the angle of view. Optionally enter a full-frame focal length to find the lens that frames the same view on your sensor.
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Result
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Worked example
A 35 mm f/1.8 lens on a Nikon/Sony APS-C sensor (23.6 × 15.6 mm, diagonal 28.3 mm): crop factor = 43.27 ÷ 28.29 = 1.53. Equivalent focal length 35 × 1.53 = 53.5 mm; equivalent aperture f/1.8 × 1.53 = f/2.75 for depth of field. To frame like a 50 mm full-frame lens you need 50 ÷ 1.53 = 32.7 mm.
How it works
Crop factor = 43.27 mm ÷ sensor diagonal, where 43.27 mm is the diagonal of a 36 × 24 mm full-frame image. Multiplying the focal length by the crop factor gives the full-frame focal length with the same field of view. To match depth of field and total light as well, the f-number is multiplied by the crop factor too: a 50 mm f/2 lens on a 2× sensor is equivalent to 100 mm f/4. The field of view is 2 × atan(dimension / (2 × f)) for focus at infinity.
Equivalence compares framing and depth of field. It does not change the lens’s real f-number for metering: f/1.8 still needs the same shutter speed at the same ISO. Sensor dimensions vary slightly between makers; pick the closest, and check your camera manual for the exact size.
Sources and basis (checked 2026-10-05): Wikipedia: Crop factor (CF = diagonal of 35 mm frame, 43.3 mm / sensor diagonal), 35 mm equivalent focal length (multiply focal length by the crop factor; 50 mm f/2 on 2× = 100 mm f/4) and Wikipedia: Image sensor format (sensor dimensions, checked 2026-10-05).
FAQ
What is crop factor?
The ratio of a full-frame sensor diagonal (43.27 mm) to your sensor diagonal. A larger crop factor means a smaller sensor.
What is the 35mm equivalent of my lens?
Multiply the focal length by the crop factor. A 35 mm lens on a 1.53 crop sensor frames like a 53.5 mm lens on full frame.
Does the aperture change on a crop sensor?
The lens keeps its marked f-number for exposure. For depth of field and noise comparisons, multiply the f-number by the crop factor to get the full-frame equivalent.
Why do APS-C sensors from different makers differ?
Canon APS-C is about 22.3 × 14.9 mm and Nikon and Sony are about 23.6 × 15.6 mm, so their crop factors are 1.61 and about 1.53.
Is the field of view exact?
It is exact for a simple lens focused at infinity. Focusing closer or lens distortion changes the real angle slightly.