Lens Power Calculator
🔍 Light & optics. Use the Lens power formula to find power, focal length: pick the value you want, type the others, and the answer updates as you go.
f in metres gives power in dioptres (D).
Power10 D
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Power | D |
| Focal length | m |
Worked example
Find the power when Focal length = 0.1 m.
Using P = 1/f: Power = 10 D.
Frequently asked questions
What is the formula for Lens power?
P = 1/f. f in metres gives power in dioptres (D).
What do the letters stand for, and what units are used?
Power in D, Focal length in m.
How do you calculate power?
Put the values into P = 1/f. For example, with Focal length = 0.1 m, power = 10 D.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (power, focal length) and fill in the others: it rearranges the formula for you.
