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 |