Focal Length Equivalent Calculator
Convert a lens focal length between full-frame (35mm) equivalent and any camera crop sensor using the crop factor multiplier.
Crop Factor and Focal Length Equivalence
When you put a lens designed for a full-frame (35mm) camera on a camera with a smaller sensor, the field of view changes. The crop factor (also called focal length multiplier) describes exactly how much narrower the view becomes.
The Formula
Full-frame equivalent = Actual focal length × Crop factor
Or, to find the actual focal length needed to achieve a given full-frame equivalent on a crop sensor:
Required focal length = Full-frame equivalent ÷ Crop factor
Common Sensor Formats and Crop Factors
| Sensor Format | Crop Factor | Example Cameras |
|---|---|---|
| Full frame (35mm) | 1.0× | Canon 5D, Nikon Z6, Sony A7 |
| APS-H | 1.3× | Some older Canon EOS-1D |
| APS-C (Canon) | 1.6× | Canon 90D, Canon M50 |
| APS-C (Nikon/Sony/Fuji) | 1.5× | Nikon D7500, Sony A6400, Fuji X-T4 |
| Micro Four Thirds | 2.0× | Olympus OM-D, Panasonic GH6 |
| 1-inch sensor | 2.7× | Sony RX100, Nikon CX |
| Smartphone (typical) | 6–8× | Varies by model |
Practical Examples
A 50mm lens on APS-C (1.5×) behaves like a 75mm on full frame — more telephoto than expected. A 35mm lens on Micro Four Thirds (2×) behaves like a 70mm — useful for portraits. To get a true 50mm “normal” perspective on APS-C, use a 33–35mm lens.
Does Aperture Change?
The maximum aperture (f-stop number) does not change — an f/1.8 lens remains f/1.8 on any sensor. However, depth of field changes: a crop sensor with the same framing as full frame produces more depth of field.
Equivalent aperture for depth of field: f/effective = f/actual × Crop factor
A 50mm f/1.8 on APS-C (1.5×) gives depth of field equivalent to 75mm f/2.7 on full frame.
Metric and Imperial — Field of View Reference
| Full-Frame Equivalent | Common Use |
|---|---|
| 14–21 mm | Ultra-wide, landscapes, architecture |
| 24–35 mm | Wide, environmental, street |
| 50 mm | “Normal” perspective, general purpose |
| 85–105 mm | Portrait, slight compression |
| 135–200 mm | Telephoto portrait, sports |
| 300 mm+ | Wildlife, sports, distant subjects |
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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