Optical Power Calculator
Calculate optical power in diopters from focal length
About this calculator
The Optical Power Calculator converts focal length measurements into optical power expressed in diopters, which is essential for optometry, ophthalmology, and lens design applications. Optical power represents a lens's ability to converge or diverge light rays, with higher diopter values indicating stronger lenses. This tool is particularly valuable for eyecare professionals prescribing corrective lenses, optical engineers designing camera systems, and students studying geometrical optics who need quick, accurate conversions between focal length and refractive power measurements.
How to use
Enter the focal length value in your preferred unit (millimeters, centimeters, or meters) into the input field. Select the appropriate unit from the dropdown menu if multiple options are available. Click the calculate button to instantly convert the focal length to optical power in diopters using the formula: Power (D) = 1/focal length (m).
Frequently asked questions
What is optical power and how is it measured?
Optical power measures a lens's ability to bend light rays, expressed in diopters (D). One diopter equals the reciprocal of focal length in meters.
How do I convert focal length to diopters?
Divide 1 by the focal length in meters. For example, a 0.5m focal length lens has 2 diopters of optical power.
What's the difference between positive and negative optical power?
Positive diopters indicate converging lenses that focus light, while negative diopters represent diverging lenses that spread light rays outward.