Diopter to Focal Length Converter
Convert optical power in diopters to focal length in metres, centimetres, and millimetres.
How to Use the Diopter to Focal Length Converter
- Enter optical power in diopters (positive or negative).
- Click Calculate to see focal length in metres, centimetres, and millimetres.
Anwendungsfälle
- •Converting eyeglass prescriptions.
- •Lens design and optics homework.
- •Photography close-up lens planning.
Formel
Focal length f = 1 / P, where P is optical power in diopters (D) and f is in metres. A +2 D lens has f = 0.5 m.
Häufig gestellte Fragen
What does a negative diopter mean?
Negative diopters indicate a diverging (concave) lens used to correct myopia. Positive diopters indicate a converging (convex) lens used for hyperopia or reading glasses.
Why 1 / P?
By definition, one diopter equals one inverse metre (m⁻¹). So optical power P and focal length f are reciprocals: P = 1/f.
Is this the same as prescription power?
Yes — spherical correction on an eyeglass prescription is in diopters and converts directly to focal length via this formula.