Crop Factor Calculator

Crop factor is the ratio between the diagonal of a 35mm full-frame sensor and the diagonal of your sensor. A larger number means a smaller sensor that captures a narrower slice of the scene through the same lens, which is why a lens looks more zoomed in on a crop body.

It takes your width and height, computes the diagonal with the Pythagorean theorem, and divides the full-frame diagonal of about 43.27 mm by that value. Full frame comes out at 1x by definition, since its diagonal divided by itself is one.

Multiply the lens focal length by the crop factor. The calculator does this for you, so a 50 mm lens on a 23.5 by 15.6 mm APS-C sensor reports 76.7 mm, meaning it frames like a 76.7 mm lens would on full frame.

Multiplying the aperture by the crop factor gives the full-frame f-number that would produce the same depth of field and a similar amount of background blur. It is a comparison aid across systems, not a setting you dial into your camera.

No. The f-number you set still governs exposure exactly as printed on the lens. The equivalent f-number only describes depth of field and total light gathered by the sensor, so an f/1.8 lens still exposes like f/1.8 whatever the body.

A 23.5 by 15.6 mm APS-C sensor is about 1.534x, Canon APS-C at 22.3 by 14.9 mm is near 1.6x, Micro Four Thirds is just under 2x, and a one-inch type sensor is roughly 2.7x. Use the presets to see each exact value.

The tool rounds each number to four significant digits for readability, so a Micro Four Thirds sensor shows 1.999x rather than a rounded 2x. That preserves the small real differences between sensors that vary by a fraction of a millimetre.

Yes. Both fields are optional. Clear either one and the matching equivalent shows a dash instead of a number, while the crop factor and sensor diagonal still calculate from the width and height alone.

Yes. The whole calculation runs in your browser with no upload, so the sensor sizes and lens details you enter never leave your device.