About the Crop Factor Calculator
This crop factor calculator converts a lens setting from one sensor size to another. Enter the focal length and aperture you are using, pick your camera’s sensor and the format you want to compare against, and it returns the equivalent focal length that gives the same angle of view, the equivalent aperture that gives the same depth of field, and the ISO that gives a similar overall noise level.
It is useful when you move between systems (for example from an APS-C body to full frame), when you read a lens review written for a different format, or when you want to know what a phone or Micro Four Thirds lens “really” behaves like in the familiar 35 mm terms most people learned on. A bar chart shows which focal length every common format would need to frame the same scene.
The calculator uses the conventional crop factors that camera makers quote (1.5× for Nikon, Sony and Fujifilm APS-C, 1.6× for Canon APS-C, 2× for Micro Four Thirds), measured against a 36 × 24 mm full-frame sensor. Exposure does not change: f/2.8 is f/2.8 for metering on any sensor — the “equivalent aperture” only describes depth of field and total light gathered.
With the default inputs, the equivalent focal length is 75 mm. Change any value above to recalculate instantly.
How to use the crop factor calculator
- 1Enter the focal length printed on your lens or shown in your photo’s EXIF data.
- 2Enter the aperture (f-number) and, optionally, the ISO you shot at.
- 3Choose your camera’s sensor format, or a custom crop factor.
- 4Choose the format you want to compare with — usually full frame.
- 5Read the equivalent focal length, aperture and ISO, and check the chart for other formats.
Formula and method
A crop factor is the ratio of the full-frame diagonal (43.27 mm for a 36 × 24 mm sensor) to another sensor’s diagonal. Multiplying a focal length by the crop factor gives the full-frame focal length with the same angle of view; to compare two non-full-frame formats, the calculator divides one crop factor by the other to get a single conversion factor k.
Multiplying the f-number by k gives the aperture that produces the same depth of field and the same total light on the sensor when the framing is matched, and multiplying ISO by k² gives a comparable noise level. The angle of view uses the rectilinear lens formula with the full-frame diagonal (or 36 mm width for the horizontal view) and the 35 mm-equivalent focal length, focused at infinity.
- f
- Actual focal length of the lens (mm)
- N
- Actual f-number
- k
- Conversion factor between the two sensor formats
- d
- Full-frame diagonal, 43.27 mm (36 mm for horizontal view)
Worked examples
50 mm f/1.8 on APS-C (1.5×) vs full frame
Multiplying by the 1.5× crop factor turns 50 mm into a 75 mm full-frame equivalent, a short-telephoto portrait view with a 32.2° diagonal angle of view. Depth of field matches f/2.7 on full frame (1.8 × 1.5), and ISO 400 looks roughly like ISO 900 (400 × 1.5²).
25 mm f/1.4 on Micro Four Thirds
Micro Four Thirds has a 2× crop factor, so a 25 mm lens frames like a 50 mm “normal” lens on full frame. Its f/1.4 aperture gives depth of field similar to f/2.8 on full frame, and ISO 200 behaves like ISO 800 for noise.
Canon APS-C lens on a Nikon APS-C body
The conversion factor between a 1.6× and a 1.5× sensor is 1.6 ÷ 1.5 = 1.067, so 18 mm on Canon APS-C frames like 19.2 mm on a 1.5× body. Both correspond to about 28.8 mm on full frame.
Frequently asked questions
What is the crop factor of APS-C?+
Nikon, Sony, Fujifilm and Pentax APS-C sensors (about 23.5 × 15.6 mm) are quoted as 1.5×, while Canon APS-C sensors (about 22.3 × 14.9 mm) are 1.6×. Micro Four Thirds is 2×, and 1-inch type sensors are about 2.7×.
Does crop factor change the actual focal length?+
No. A 50 mm lens is always 50 mm. A smaller sensor simply records a smaller central part of the image circle, so the field of view matches a longer lens on full frame.
Do I need to multiply the aperture by the crop factor for exposure?+
No. f/2.8 delivers the same light per unit area — and therefore the same shutter speed and ISO for a correct exposure — on every sensor. The equivalent aperture only describes depth of field and total light, which affects noise.
Why does a phone camera have such a large crop factor?+
Phone main cameras use sensors roughly 6–10 mm wide, so the crop factor is often 4× to 7×. That is why a phone lens marked 6 mm can behave like a 24–26 mm wide-angle lens on full frame.
Can I use full-frame lenses on an APS-C camera?+
Usually yes, if the mount matches. The lens works normally, but because of the crop the field of view narrows — a 24–70 mm full-frame zoom frames like 36–105 mm on a 1.5× body.