Camera Sensor Crop Factor Calculator
Free crop factor calculator: find your sensor crop factor and the 35mm-equivalent focal length and aperture for any lens, with the diagonal formula shown.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Crop Factor Calculator Works
Crop factor compares your camera’s sensor to a full-frame 35mm sensor so you can predict how a lens will actually frame. Choose your sensor format (or enter a custom size), then add a focal length and aperture to see the crop factor, the 35mm-equivalent focal length, and the equivalent aperture for depth of field.
The Formula
Crop factor is the ratio of the full-frame diagonal to your sensor’s diagonal:
Crop factor = 43.27 mm / sensor diagonal Equivalent focal length = focal length × crop factor Equivalent aperture (depth of field) = aperture × crop factor
The 43.27 mm comes from a full-frame sensor measuring 36 × 24 mm: √(36² + 24²) = 43.27 mm.
Worked Example
A 50mm f/1.8 lens on a 1.5x APS-C body (23.5 × 15.6 mm sensor):
- Sensor diagonal = √(23.5² + 15.6²) = 28.2 mm
- Crop factor = 43.27 ÷ 28.2 = ≈ 1.53x (commonly rounded to 1.5x)
- Equivalent focal length = 50 × 1.5 = 75 mm field of view
- Equivalent aperture = f/1.8 × 1.5 = f/2.7 for depth of field
So your 50mm f/1.8 frames like a 75mm lens and renders background blur like an f/2.7 lens would on full frame, while still letting in as much light as f/1.8 for exposure.
Common Sensor Crop Factors
| Sensor format | Approx. size | Crop factor |
|---|---|---|
| Full frame | 36 × 24 mm | 1.0x |
| APS-C (Nikon/Sony/Fuji) | 23.5 × 15.6 mm | 1.5x |
| APS-C (Canon) | 22.3 × 14.9 mm | 1.6x |
| Micro Four Thirds | 17.3 × 13 mm | 2.0x |
| 1-inch | 13.2 × 8.8 mm | 2.7x |
Use the equivalent focal length to choose a lens for a given field of view, and the equivalent aperture to compare how much subject-background separation different camera-and-lens combinations will deliver.
Frequently asked questions
What is crop factor?+
Crop factor is the ratio of a full-frame 35mm sensor's diagonal to your camera's sensor diagonal. It tells you how much narrower your field of view is than full frame, so a lens on a smaller sensor frames like a longer lens would on full frame.
How do I calculate crop factor?+
Divide the full-frame diagonal of 43.27mm by your sensor's diagonal. For an APS-C sensor measuring 23.5 × 15.6mm, the diagonal is about 28.2mm, so the crop factor is 43.27 ÷ 28.2 ≈ 1.5x.
How do I find the equivalent focal length?+
Multiply the lens focal length by the crop factor. A 50mm lens on a 1.5x APS-C body gives a 50 × 1.5 = 75mm equivalent field of view, framing the scene like a 75mm lens would on full frame.
Does crop factor change the aperture?+
It does not change the f-number you set for exposure, so brightness stays the same. But for depth of field and total light gathered, the equivalent aperture is the f-number times the crop factor: f/1.8 on a 1.5x sensor behaves like f/2.7 on full frame.
Which sensors have which crop factors?+
Full frame is 1.0x, Nikon, Sony and Fuji APS-C are about 1.5x, Canon APS-C is 1.6x, Micro Four Thirds is 2.0x and a 1-inch sensor is about 2.7x. Larger crop factors mean a smaller sensor and a narrower field of view.