Diopter Calculator

Convert focal length to lens power in diopters.

Power (D) 2

Formula: P = 1 ÷ f

Step-by-step with your numbers:

1. Values used:

2. Focal length = 0.5

4. Power = 2D

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Lens power in diopters is the reciprocal of the focal length in metres.

The math behind it

P = 1/f. A 0.5 m focal length is +2 D; shorter focal lengths give stronger lenses.

f = 0.5 m → +2 diopters.

What does a negative diopter mean?

A diverging (concave) lens, used to correct nearsightedness.