Equivalent focal length calculator
Work out what any lens becomes on a 35mm full-frame camera, or reverse the maths - enter the equivalent you want and find the real lens you need for your sensor.
Conversion
Picking a preset sets the crop factor from real sensor dimensions.
Need a bare number instead? The crop factor here is the diagonal ratio against full frame - see the crop factor calculator for the details.
Result
Converted focal length
Equivalent focal length reproduces full-frame diagonal angle of view.
How it works
Every sensor has a crop factor - the ratio of its diagonal to the 36 × 24 mm full-frame diagonal (43.27 mm). To find the full-frame equivalent of any lens you simply multiply:
The reverse direction is the same relationship solved the other way:
This is why a 25 mm lens on Micro Four Thirds (×2.0) frames like a 50 mm on full frame, even though it is still physically a 25 mm lens with the same perspective and depth-of-field behaviour at a given aperture.
Example
A 50 mm lens on an APS-C Canon body (22.3 × 14.9 mm, crop factor 1.61×) is equivalent to 50 × 1.61 = 80.7 mm on full frame. Reversing: to match a classic 85 mm portrait look on that body you would want an actual focal length near 85 ÷ 1.61 ≈ 53 mm.
Common conversions
- APS-C (Nikon/Sony/Fuji), crop 1.53×: a 35 mm lens behaves like ~54 mm.
- APS-C Canon, crop 1.61×: a 35 mm lens behaves like ~56 mm.
- Micro Four Thirds, crop 2.00×: a 25 mm lens behaves like 50 mm.
- 1-inch, crop 2.73×: a 10 mm lens behaves like ~27 mm.
Related tools
See where the crop factor comes from in the crop factor calculator, or compare actual angles with the field of view calculator. Starting from a desired framing instead? Solve backwards with the focal length calculator.
Frequently asked questions
What is a full-frame equivalent focal length?
It is your lens's actual focal length multiplied by your sensor's crop factor. It tells you which focal length on a 36 × 24 mm full-frame camera would capture the same angle of view. The lens itself never changes.
How do I convert back from equivalent to actual focal length?
Divide the full-frame equivalent by the crop factor. For example, an 80 mm full-frame equivalent on a 2× Micro Four Thirds camera is a real 40 mm lens.
Is equivalent focal length the same as field of view?
Not exactly - it is a convenient proxy. Equivalent focal length matches the diagonal angle of view of full frame, which is how camera makers quote crop factor. Horizontal and vertical framing can still differ slightly between aspect ratios.