Crop Factor Calculator
Convert a lens focal length and aperture to its full-frame equivalent for any sensor size.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Crop factor compares a sensor diagonal against full frame, and it applies to focal length and aperture but not to exposure. That is why a 50 mm f/2 lens on a micro four thirds body frames like a 100 mm f/4 on full frame while still admitting the same light per unit area.
Worked example
calculated with the default values below
Sensor size APS-C (Nikon, Sony, Fuji) · Lens focal length 50 mm · Aperture 1.8 f/ · Subject distance 5 m Full-frame equivalent focal length 75.0 mm · Equivalent aperture for depth of field 2.70 f/ · Crop factor 1.50 · Diagonal angle of view 32.18 degrees · Diagonal coverage at distance 2.88 m · Sensor diagonal 28.84 mm
General background references
Disclaimer
These calculators give general estimates. Sizing, pricing, availability and standards vary by brand, retailer and country, so treat the output as a starting point and confirm it against the seller's or authority's own figures.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
f_eq = f × c; θ = 2 × atan(43.2666 ÷ (2 × c × f)) × 180 ÷ π
- c
- Crop factor
- f
- Focal length (mm)
- d
- Subject distance
- θ
- Diagonal angle of view (°)
Diagonal sensor size = 43.2666 mm ÷ crop factor; diagonal angle of view and diagonal field of view follow from that diagonal. Horizontal width requires a sensor aspect ratio, which is not an input. Equivalent aperture is a depth-of-field comparison.
Frequently asked questions
Why does it show diagonal field of view instead of width?
The selected crop factor identifies sensor diagonal only. Without a sensor aspect ratio, horizontal width cannot be determined, so the calculator reports diagonal field of view. Equivalent aperture is a depth-of-field comparison; crop factor does not change the lens f-number used for exposure.