Crop Factor Calculator

How to use

1. 1Choose Lens on a sensor, then pick your camera sensor from the list or enter a custom width and height in millimetres.
2. 2Type the focal length printed on the lens, for example 50, to get the full-frame equivalent focal length and the angle of view.
3. 3Optionally enter the aperture as an f-number to also see the equivalent aperture for depth of field and total light.
4. 4Switch to Compare two sensors to pick a first and second sensor and read the focal length that frames the same scene on the second one.
5. 5Copy the summary for your notes, or reset to return every field to its starting values.

About this tool

Crop Factor Calculator translates a lens between sensor sizes so you can compare cameras and lenses on equal terms. Every interchangeable-lens camera has a sensor, and the size of that sensor decides how much of the scene a given lens actually captures. The crop factor is the single number that captures the difference: it is the ratio of the 35mm full-frame diagonal, about 43.27 mm for a 36 x 24 mm frame, to your sensor's own diagonal. A smaller sensor has a larger crop factor and records a narrower slice of the image circle, which is why a 50 mm lens looks more zoomed-in on a crop body than on full frame. The tool turns that crop factor into the three answers photographers search for. First is the full-frame equivalent focal length, the real focal length multiplied by the crop factor, which tells you which 35mm lens frames the same field of view: a 50 mm lens on a 1.5x APS-C body frames like a 75 mm lens on full frame, and a 25 mm lens on a 2x Micro Four Thirds body frames like a 50 mm normal lens. The real focal length printed on the barrel never changes; only the captured angle of view does, and stating the equivalent is the only fair way to compare framing across formats. Second is the equivalent aperture, the f-number multiplied by the same crop factor, used to compare depth of field and the total light gathered for an equivalent framing. f/2.8 on a 2x crop sensor renders the depth of field and the whole-frame light of f/5.6 on full frame, which is why larger sensors are prized for background separation. This is a depth-of-field and total-light comparison only: f/2.8 still meters as f/2.8 for shutter speed and ISO, so the exposure brightness is unchanged. Third is the angle of view, computed directly from the real focal length and the sensor dimensions with the rectilinear model AOV = 2 x arctan(dimension / (2 x focal length)), and reported across the diagonal, the horizontal width, and the vertical height so you know exactly how wide the shot is. A second mode compares any two sensors head to head, from full frame against APS-C to a phone sensor against Micro Four Thirds, and reports the relative crop and the focal length on the second sensor that frames the same scene as a chosen focal length on the first, which is the calculation behind adapting a lens or switching systems. Presets cover medium format, full frame, APS-H, both common APS-C sizes, Micro Four Thirds, 1 inch, Super 16, and several compact and phone sensor sizes, and a custom option accepts any width and height in millimetres so unusual or cinema sensors work too. Every figure is computed in your browser with plain trigonometry and ratios. The camera, lens, and sensor values you enter never leave your device and no lookups are made.

Free to use. Works in your browser. No signup, no login.