Crop Factor Calculator

Crop factor is full-frame diagonal over your sensor diagonal. Multiply the barrel focal length by that number to talk 35 mm-equivalent field of view. It does not magically add reach in resolution — it just describes a smaller window on the same image circle.

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Results

Sensor diagonal: 28.21mm
Crop factor: 1.534×
35 mm-equivalent focal length: 53.7mm

Recommended gear

IBIS camera body
Full-frame and APS-C IBIS bodies do not share crop. Check the sensor millimetres in the spec sheet, not the marketing name.
Typical range: $800–$2,500
Fast wide prime
A 23 mm on APS-C is a 35 mm-ish view. Buy the barrel number that gives the equivalent you actually want.
Typical range: $200–$800

Calculation method

Sensor diagonal is the hypotenuse of width and height. Crop factor is the 36×24 mm full-frame diagonal (about 43.27 mm) divided by that. Equivalent focal length is barrel focal length times crop. A 35 mm lens on 1.5× APS-C frames like a 52.5 mm on full frame. Canon APS-C is often ~1.6× because the sensor is a bit smaller.

Exact formula

diagonal = √(w²+h²). crop = hypot(36,24) / diagonal. equivalent focal = f × crop. Limits: Aspect-ratio crops, anamorphic squeeze and digital teleconverters omitted; full frame is 36×24 mm.

Micro Four Thirds

17.3×13 mm is a 2× crop. A 25 mm f/1.8 frames like a 50 mm and, for DoF, behaves more like f/3.6 on full frame — see equivalent aperture.

Medium format

A 44×33 mm back has crop around 0.79×. Equivalent focal length is shorter than the barrel. The same formula still holds.

Frequently asked questions

Does crop add megapixels of reach?

No. You are using the middle of the image circle. A 300 mm on APS-C looks like 450 mm, but you have fewer millimetres of sensor collecting that view than a 450 mm on full frame.

Speed booster?

A 0.71× reducer on APS-C nearly cancels a 1.5× crop for field of view and gathers more light. This calculator is the naked sensor versus 36×24 mm.

Square crop in camera?

You changed the aspect, so the diagonal of the used rectangle changed. Type the cropped width and height, not the full sensor.

Disclaimer — no professional advice, no liability

Equivalent focal length is a field-of-view comparison, not a depth-of-field or noise comparison. Pair it with equivalent aperture if you are matching a look across formats.

These calculators, pages and any related content are provided “as is” and “as available”, solely for general educational and informational purposes. They are simplified mathematical estimates, not a light-meter reading, a studio plot or a shooting prescription, and they do not constitute professional photographic, cinematographic or optical advice.

Results can be wrong, incomplete or inapplicable to your camera, lens, sensor, filter, lighting or use case. You must independently verify every figure, assume all risk, and confirm settings on a test shot before a job that can miss the image, damage gear or injure someone.

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Crop Factor Calculator

Inputs

Results

Recommended gear

Calculation method

Exact formula

Micro Four Thirds

Medium format

Frequently asked questions

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Field of View Calculator

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