Crop Factor Calculator (Equivalent Focal Length and Aperture)
Enter the lens focal length and aperture and choose the sensor.
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Crop Factor Calculator (Equivalent Focal Length and Aperture) by TheCalcTools
How the Crop Factor Calculator (Equivalent Focal Length and Aperture) works
Crop factor is the ratio of a full-frame diagonal (43.3 mm) to the sensor’s diagonal. Multiplying the focal length by it gives the full-frame lens with the same field of view.
For the same framing and print size, depth of field matches a full-frame lens at f-number × crop factor. Exposure (brightness) depends only on the actual f-number.
The formula
Worked example
Using the default values shown in the calculator:
| Focal length (mm) | 35 |
|---|---|
| Aperture (f-number) | 1.8 |
| Sensor | APS-C Nikon/Sony/Fuji (23.5 × 15.6 mm) |
- 35 mm f/1.8 on APS-C (crop 1.53) frames like 53.6 mm on full frame, with the depth of field of f/2.8.
Result:
| Crop factor | 1.53 |
|---|---|
| Full-frame equivalent focal length (mm) | 53.6 |
| Equivalent aperture for depth of field | f/2.8 |
| Exposure | Exposure is still f/1.8: the crop factor does not change brightness |
Frequently asked questions
Is a 35 mm lens on APS-C a 50 mm lens?
It frames like a 52 to 56 mm lens on full frame, but it is still optically a 35 mm lens.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.