Use this tool to quickly convert focal length between different camera sensor formats. If you shoot with APS-C, Micro Four Thirds, full frame, medium format, or even compact/smartphone sensors, equivalent focal length helps you compare lenses in a consistent way.
What “equivalent focal length” means
Equivalent focal length is a comparison system. It does not change the physical focal length of your lens. A 50mm lens is always 50mm. What changes is the field of view you get, because different sensor sizes capture a larger or smaller portion of the lens image circle.
Most photographers use full frame (35mm format) as the reference point. So when someone says a lens “looks like a 75mm,” they usually mean it gives a field of view similar to a 75mm lens on full frame.
Core formulas
35mm/full-frame equivalent
Equivalent focal length = actual focal length × crop factor
- 35mm on APS-C (1.5x) → 52.5mm equivalent
- 25mm on Micro Four Thirds (2.0x) → 50mm equivalent
- 80mm on medium format (0.79x) → 63.2mm equivalent
Converting between two sensor formats
Target focal length for same framing = (source focal length × source crop) ÷ target crop
Example: 35mm on APS-C 1.5x to Micro Four Thirds 2.0x:
- 35 × 1.5 = 52.5mm full-frame equivalent
- 52.5 ÷ 2.0 = 26.25mm on Micro Four Thirds for similar framing
Common crop factors
- Full frame: 1.0x
- APS-C (Nikon/Sony/Fuji): 1.5x
- APS-C (Canon): 1.6x
- Micro Four Thirds: 2.0x
- 1-inch sensor: 2.7x
- Medium format (Fujifilm GFX): ~0.79x
How to use this calculator effectively
1) Enter your real lens focal length
Type the lens number printed on the barrel (for zooms, choose one value in the zoom range).
2) Select source and target formats
The source is the camera you are using now; the target is what you want to compare against.
3) Add aperture if you want depth-of-field equivalence
Equivalent aperture is useful when comparing background blur between formats. The calculator will report an approximate full-frame equivalent aperture and target-format equivalent aperture for similar framing and depth of field.
Practical lens planning examples
- Street photography: 23mm on APS-C (1.5x) behaves like ~35mm equivalent.
- Portraits: 42.5mm on Micro Four Thirds gives about an 85mm equivalent field of view.
- Travel setup: 16-50mm on APS-C roughly covers 24-75mm equivalent.
Important notes
- Equivalent focal length compares field of view, not magnification in an absolute optical sense.
- Perspective is controlled by camera-to-subject distance, not sensor size directly.
- Depth-of-field equivalence assumes matched framing and viewing conditions.
FAQ
Does crop factor make my lens “longer”?
No. The lens focal length is unchanged. The sensor crops the image, making the field of view narrower.
Why use full-frame equivalent at all?
It gives photographers a shared language for comparing composition across systems.
Can I use this for video too?
Yes. The same crop-factor math applies, but remember some cameras add extra crop in specific video modes.