Crop Factor Calculator
The crop factor of a camera sensor, the full-frame equivalent focal length and aperture of a lens, and the pixel pitch and megapixels from the sensor size and resolution.
Result…
How it's calculated
Crop factor = 43.27 mm ÷ sensor diagonal (43.27 mm = √(36² + 24²), the full-frame diagonal) Sensor diagonal = √(width² + height²) Equivalent focal length = focal length × crop factor Equivalent aperture (depth of field) = f-number × crop factor Pixel pitch (µm) = sensor width (mm) × 1000 ÷ horizontal pixels Megapixels = horizontal pixels × vertical pixels ÷ 1,000,000
Works out how much smaller (or larger) a sensor is than full frame by comparing diagonals: crop factor = 43.27 mm ÷ the sensor diagonal, the definition given in Wikipedia's image sensor format article, where the preset sensor sizes also come from. Multiply a lens's focal length by the crop factor for the full-frame focal length with the same angle of view, and its f-number by the crop factor for the aperture that gives the same depth of field on full frame. From the image size in pixels it also finds the pixel pitch, the distance between the centres of neighbouring pixels in micrometres, and the megapixel count.
Your numbers, step by step
About the Crop Factor calculator
This crop factor calculator compares your camera's sensor with a full-frame 36 × 24 mm sensor. Pick a format such as APS-C, Micro Four Thirds or 1-inch type, or enter your own sensor's width and height, and it divides the full-frame diagonal of 43.27 mm by your sensor's diagonal. From that it gives the full-frame equivalent focal length of your lens, so you can compare framing across systems, and the equivalent aperture for the same depth of field and background blur. Enter the image size in pixels and it also works out the pixel pitch in micrometres and the megapixel count. It is useful when choosing lenses for a new camera, comparing compact cameras and phones, or reading reviews that quote equivalent figures. Every step of the working is shown with your numbers.
How to use it
- Pick your “Sensor format”, or “Enter the sensor size” in millimetres.
- Enter the “Focal length” and “Aperture (f-number)” of your lens.
- Enter the “Horizontal pixels” and “Vertical pixels” from the camera's specification.
- Read the crop factor, the equivalent focal length and aperture, the pixel pitch and the megapixels.
Worked example
A Micro Four Thirds camera (17.3 × 13 mm sensor) with a 25 mm f/1.8 lens and a 5184 × 3888 pixel image. The sensor diagonal is √(17.3² + 13²) = 21.64 mm, so the crop factor is 43.27 ÷ 21.64 = 2.00. The lens frames like a 25 × 2.00 = 49.98 mm lens on full frame and gives the depth of field of f/3.6 there. Pixel pitch = 17.3 × 1000 ÷ 5184 = 3.34 µm, and 5184 × 3888 = 20.16 megapixels.
Updated
Questions people ask
How do I calculate the crop factor of a sensor?
Work out the sensor diagonal as √(width² + height²), then divide 43.27 mm, the diagonal of a 36 × 24 mm full-frame sensor, by it. This is the definition given in Wikipedia's image sensor format article.
What is the formula for equivalent focal length?
Multiply the real focal length by the crop factor. A 35 mm lens on an APS-C sensor with a crop factor of 1.53 frames like a 53.5 mm lens on full frame.
Does a crop factor change the exposure of my aperture?
No. An f/1.8 lens gives the same exposure on any sensor; the equivalent aperture only describes the depth of field and background blur you would get on full frame for the same framing. Use the exposure calculator for shutter speed and ISO.
What is pixel pitch and why does it matter?
It is the distance between the centres of neighbouring pixels, the sensor width divided by the number of pixels across. Larger pixels gather more light each, while smaller ones record finer detail if the lens can resolve it.
Why do different sources give slightly different crop factors?
Sensors of one format vary by a few tenths of a millimetre between makers and models, and some sources round the full-frame diagonal to 43.3 mm. Enter your camera's exact sensor size for its own figure.
Is the crop factor exact for every sensor shape?
It compares diagonals, so a 4:3 sensor frames a little differently across its width than a 3:2 sensor with the same factor. The field of view calculator gives the angles across the width and height.