Equivalent Focal Length Calculator
Crop factor, equivalent focal length, equivalent aperture and equivalent ISO for any sensor size.
Results
Equivalent focal length on 35 mm
53.69
mm
Crop factor
1.5339
Equivalent f-number
3.068
Equivalent ISO
941
Sensor diagonal
28.2066
mm
Stops of difference
1.234
Sensor aspect ratio
1.5064
Focal needed on this sensor for the same view
22.82
mm
What this tool does
Equivalence is often given only for focal length, which tells half the story. The same crop factor that turns 35 mm into a 53 mm view also turns f/2 into the depth of field and the light-gathering of f/3, and ISO 400 into the noise of ISO 941 — because the smaller sensor collects proportionally less light in total. All three are shown here, with the stops of difference, so the comparison is a fair one.
Formula
crop factor = 43.267 ÷ sensor diagonal · equivalent focal = focal × factor · equivalent aperture = N × factor · equivalent ISO = ISO × factor²
Variables
| Symbol | Meaning | Unit |
|---|---|---|
sw | Sensor width | mm |
sh | Sensor height | mm |
fl | Focal length as marked | mm |
ap | f-number | — |
iso | ISO | — |
EF | Equivalent focal length on 35 mm | mm |
CF | Crop factor | — |
EA | Equivalent f-number | — |
EI | Equivalent ISO | — |
SD | Sensor diagonal | mm |
ST | Stops of difference | — |
AR | Sensor aspect ratio | — |
BF | Focal needed on this sensor for the same view | mm |
Worked example
- Sensor width23.5 mm
- Sensor height15.6 mm
- Focal length as marked35 mm
- f-number2
- ISO400
- Equivalent focal length on 35 mm53.69 mm
- Crop factor1.5339
- Equivalent f-number3.068
- Equivalent ISO941
- Sensor diagonal28.2066 mm
- Stops of difference1.234
- Sensor aspect ratio1.5064
- Focal needed on this sensor for the same view22.82 mm
Limitations
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.