# Optical power of a lens

P = 1/{f}
Calculation of the optical power of a lens.
Enter 'x' in the field to be calculated.

This tool calculates the optical power of a lens based on the focal length.

P: power in delta (diopter)
f: focal length in meter

P = 1/f

## What is the optical power of a lens

The optical power of a lens is its ability to deviate the rays of light. It is equal to the reciprocal of the focal length and is expressed in delta (diopter or dioptre) which is equivalent to m^{-1}. By convention, the power of a converging lens is positive while the power of a diverging lens is negative.

The lower is the focal distance (in absolute value), the more 'powerful' the lens is and the more it deviates the rays of light.

The above formula can be generalized to any optical system immersed in vacuum or air (refractive index n = 1).