Lens Equivalent Calculator

A lens's focal length never changes when you move it between cameras, but the field of view it produces does, because smaller sensors only capture the middle slice of the same projected image circle. This calculator handles that by computing each sensor's crop factor as the ratio of a full-frame sensor's diagonal (43.27mm, the 36×24mm reference) to the source and target sensors' own diagonals, using a lookup table of standard sensor sizes from Micro Four Thirds up to medium format. Your entered focal length is first converted to its full-frame-equivalent focal length by multiplying by the source crop factor, then converted back down to the target sensor by dividing by the target crop factor — effectively routing the conversion through full frame as a common reference, which is the standard way equivalence is expressed across the industry. The Conversion Factor is simply the ratio of the two sensors' diagonals directly, letting you skip the full-frame detour if you already know your source and target sizes.

Field of view is estimated from the diagonal measurement of each sensor using the standard 2·atan(sensor/2f) formula, and the full-frame-equivalent focal length also drives a lens-category label (wide, normal, telephoto, and so on) so you can sanity-check the result against how the shot will actually feel. The biggest caveat: this only reproduces angle of view, not depth of field, aperture, or light-gathering behavior — a 50mm f/1.8 on Micro Four Thirds frames like a 100mm lens but still has the depth-of-field and exposure characteristics of an actual 50mm f/1.8, so "equivalent" here is strictly about framing, not the full optical picture some equivalence calculators try to capture. Sensor diagonals are approximate nominal values, not measured from your specific camera model, so results near category boundaries (e.g., wide vs. normal) should be treated as close estimates.