Focal Length Equivalent Calculator
Calculate focal length equivalent from the published formulas and tables for the craft.
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What this tool does
Calculate focal length equivalent from the published formulas and tables for the craft. Sensor dimensions are the manufacturers' published nominal sizes. Crop factor compares diagonals; the equivalent aperture describes depth of field only — exposure f-numbers do not change with sensor size.
How to use the Focal Length Equivalent Calculator
- Enter or select lens focal length (mm).
- Enter or select lens aperture (f-number).
- Enter or select sensor format.
- Read the calculated result; change any measurement to compare alternatives.
Formula
crop factor = 43.27 mm (full-frame diagonal) ÷ sensor diagonal; 35mm-equivalent focal = focal × crop; horizontal FOV = 2 × atan(sensor width ÷ (2 × focal)); full-frame-equivalent aperture for depth of field = f-number × crop
- focal
- Lens focal length (mm)
- aperture
- Lens aperture (f-number)
- sensor
- Sensor format
Sensor dimensions are the manufacturers' published nominal sizes. Crop factor compares diagonals; the equivalent aperture describes depth of field only — exposure f-numbers do not change with sensor size.
Worked example
For focal length equivalent calculator, the following measurements illustrate the exact method: Lens focal length (mm): 35; Lens aperture (f-number): 2.8; Sensor format: aps-c-sony-nikon.
Inputs
- Lens focal length (mm)35
- Lens aperture (f-number)2.8
- Sensor formatSony / Nikon / Fujifilm APS-C 23.5 × 15.6 mm
Result
- 35mm-equivalent focal length (mm)53.69
- Crop factor1.53
- Horizontal field of view (degrees)37.12
- Vertical field of view (degrees)25.13
- Diagonal field of view (degrees)43.89
- Full-frame-equivalent aperture for depth of field (f/)4.3
Results explained
- 35mm-equivalent focal length (mm)
- 35mm-equivalent focal length (mm) from the formula above. Sensor dimensions are the manufacturers' published nominal sizes. Crop factor compares diagonals; the equivalent aperture describes depth of field only — exposure f-numbers do not change with sensor size.
- Crop factor
- Crop factor from the formula above. Sensor dimensions are the manufacturers' published nominal sizes. Crop factor compares diagonals; the equivalent aperture describes depth of field only — exposure f-numbers do not change with sensor size.
- Horizontal field of view (degrees)
- Horizontal field of view (degrees) from the formula above. Sensor dimensions are the manufacturers' published nominal sizes. Crop factor compares diagonals; the equivalent aperture describes depth of field only — exposure f-numbers do not change with sensor size.
- Vertical field of view (degrees)
- Vertical field of view (degrees) from the formula above. Sensor dimensions are the manufacturers' published nominal sizes. Crop factor compares diagonals; the equivalent aperture describes depth of field only — exposure f-numbers do not change with sensor size.
- Diagonal field of view (degrees)
- Diagonal field of view (degrees) from the formula above. Sensor dimensions are the manufacturers' published nominal sizes. Crop factor compares diagonals; the equivalent aperture describes depth of field only — exposure f-numbers do not change with sensor size.
- Full-frame-equivalent aperture for depth of field (f/)
- Full-frame-equivalent aperture for depth of field (f/) from the formula above. Sensor dimensions are the manufacturers' published nominal sizes. Crop factor compares diagonals; the equivalent aperture describes depth of field only — exposure f-numbers do not change with sensor size.
Frequently asked questions
Multiply the lens focal length by the sensor's crop factor — the ratio of the full-frame diagonal (43.27 mm) to your sensor's diagonal. A 35 mm lens on Sony/Nikon APS-C (crop ≈1.53) frames like a 54 mm lens on full frame.
From the published dimensions: full frame 1.0×, Canon APS-C ≈1.61×, Sony/Nikon/Fujifilm APS-C ≈1.53×, Micro Four Thirds ≈2.0×, 1-inch type ≈2.7×, and 44 × 33 mm medium format ≈0.79× (it is larger than full frame, so equivalents get shorter).
No. An f/2.8 lens exposes at f/2.8 on any sensor. Crop factor only scales the equivalent aperture for depth-of-field comparisons: f/2.8 on APS-C (≈1.53×) gives depth of field like about f/4.3 on full frame at the equivalent focal length.
It frames similarly to about a 76–80 mm full-frame lens (50 × ≈1.53), so the composition matches, but perspective is set by camera position, and background blur follows the equivalent aperture — it will not blur exactly like a real 85 mm f/1.8 on full frame.
Because the tiny sensor's crop factor is large (around 4–5× for a main phone sensor), marketing converts to the full-frame focal length photographers recognise. This calculator does the same conversion for interchangeable-lens formats.