[ Sensor Size ] How to Convert Sensor Size to Sensor Diagonal?

The sensor size as specified in inches (e.g. 1/2", 1”) can be a confusing specification. It does not in fact refer to the diagonal size of the camera sensor. The physical dimensions of the camera sensor can be found in the ‘Effective Area’ specification, or through multiplying the pixel size in the X dimensions by the number of pixels in X, and vice versa for Y.

The ‘Sensor Size’ specification is in fact an industry standard specification referring to the size of a tube lens that would be suited to the sensor. Though it does correlate with the physical dimension of the sensor, a 1” ‘Sensor Size’ specification does not mean that the sensor diagonal will be exactly 1”. Further, as rounding is typically applied to the ‘Sensor Size’ specification, some error will be introduced.

A table of common values and their corresponding approximate diagonal size in mm is included below. To calculate the approximate diagonal size of the sensor from the ‘Sensor Size’ specification, the formulas below must be used, though note that which formula to use depends on the value of the ‘Sensor Size’ specification for historical reasons.