Photography Math: Exposure, Depth of Field and Crop Factor
The numbers that sharpen your photography — the exposure triangle, exposure value, depth of field and hyperfocal distance, crop factor, flash guide numbers and print size.
Crop Factor Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Full-frame equivalent focal length
75.0
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Crop Factor Calculator
The Crop Factor Calculator works out your full-frame equivalent focal length in an instant. Enter lens focal length and crop factor and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the lens focal length.
- Enter the crop factor.
- Read off your full-frame equivalent focal length — the calculator updates automatically, with no button to press.
Formula
The Crop Factor Calculator uses the formula:
Full-frame equivalent focal length = Lens focal length × Crop factor
Worked example
For example, with lens focal length of 50 mm and crop factor of 1.5, the full-frame equivalent focal length is 75.0.
| Lens focal length | 50 mm |
|---|---|
| Crop factor | 1.5 |
| Full-frame equivalent focal length | 75.0 |
|---|
Results are estimates for educational use, not professional advice.
Frequently asked questions
Multiply the lens focal length by the crop factor. A 50 mm lens on a 1.5× crop sensor behaves like a 75 mm lens on full frame.
Crop factor compares a sensor's size to full frame. Smaller sensors crop the view, making lenses act more telephoto.
APS-C is about 1.5× (1.6× for some brands), Micro Four Thirds is 2×, and full frame is 1×.
No. The lens stays the same; only the field of view changes. Equivalent focal length describes how the view compares to full frame.
The Crop Factor Calculator uses the formula: Full-frame equivalent focal length = Lens focal length × Crop factor. For example, with lens focal length of 50 mm and crop factor of 1.5, the full-frame equivalent focal length is 75.0.
Enter the lens focal length. Enter the crop factor. Read off your full-frame equivalent focal length — the calculator updates automatically, with no button to press.
Related guides
Crop Factor Table: Full-frame equivalent focal length by Lens focal length
Reference table of full-frame equivalent focal length for Crop Factor across a range of lens focal length values — exact, engine-computed figures you can read off at a glance.
How to Calculate Crop Factor: Formula, Steps & Examples
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Megapixel Table: Megapixels by Width in pixels
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