ConverterHub

Crop Factor Calculator

Find the 35mm-equivalent focal length and aperture for your sensor.

Result

53 mm
f/2.70

How it is calculated

Both values are multiplied by the sensor crop factor: equivalent focal length = focal × crop and equivalent aperture = f-number × crop. focal is the lens focal length in millimetres, aperture is the f-number (1.8 for f/1.8), and crop is the sensor's crop factor, which you type as a number (about 1.5 for many APS-C bodies, 1.6 for Canon APS-C, 2.0 for Micro Four Thirds; there is no sensor menu). The focal length is rounded to a whole millimetre, the aperture shows two decimals with an "f/" prefix. Aperture is optional: if you leave it empty, only the focal length is returned. Focal length and crop factor must be above zero. The equivalent aperture is meant for comparing depth of field and noise, not for exposure: the exposure settings stay the same.

Worked example

A 35 mm f/1.8 lens on an APS-C camera with a crop factor of 1.5. Equivalent focal length: 35 × 1.5 = 52.5, shown as 53 mm. Equivalent aperture: 1.8 × 1.5 = f/2.70. So the picture looks like a 53 mm lens would give on full frame, with the depth of field of about f/2.7 at the same framing. The lens still meters like f/1.8 for shutter speed and ISO.

Try this example →

Common mistakes

  • Believing the lens physically changes. The focal length stays 35 mm; the smaller sensor only crops the image circle, so the field of view matches a longer full-frame lens.
  • Using the equivalent f-number to set exposure. Shutter speed and ISO still follow the real f/1.8; the equivalent value is for depth-of-field and light-gathering comparisons.
  • Applying the crop factor to a lens that was designed for the smaller sensor and then multiplying twice. Multiply once, using the actual focal length printed on the lens.
  • Typing the sensor name or ratio such as "APS-C" or 3:2 into the crop field. It expects a number, for instance 1.5 or 2.
  • Using the wrong factor for a brand: Canon APS-C is about 1.6, most other APS-C is about 1.5.

About this calculator

This calculator converts a lens's focal length and aperture to their 35mm (full-frame) equivalents using the camera's sensor crop factor — the ratio between a full-frame sensor's diagonal and the actual sensor's diagonal. For example, an APS-C sensor typically has a crop factor of 1.5 (Nikon, Sony) or 1.6 (Canon), while Micro Four Thirds sensors use 2.0.

Photographers use this to predict field of view and depth of field when switching between camera systems: a 50mm lens on an APS-C body frames a scene like a 75mm lens would on full frame. It also affects effective aperture for depth-of-field comparisons, which matters when choosing gear or comparing specs across brands. Enter the focal length and your sensor's crop factor (from the examples above or your camera's specifications) to get the equivalent focal length; add the aperture as well to get the equivalent aperture.

Was this helpful?

You can pick up to 3 reactions.

Comments (0)

  • Be the first to comment.

Popular calculators

Loan Calculator

Monthly payment, total interest and full amortization schedule.

Percentage Calculator

Percent change, percent of, and ratio calculations.

Discount Calculator

Calculate final price, savings, and discount amount.

BMI Calculator

Body mass index from height and weight (metric or imperial).

Age Calculator

Compute your exact age in years, months and days from a birth date.

Compound Interest Calculator

Calculate the final amount and interest earned with compounding.

All Calculators