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Diopter Calculator
Convert focal length to lens power in diopters, and back. Optical information only.
target Free Online Tool
โก Instant Results
๐ Clear Comparison
๐ 100% Free Tool
Power from focal length
Compare Your Options And Get Clear Answers
Convert focal length to lens power in diopters, and back. Optical information only.
Diopter Estimator
Enter your numbers below for an instant estimate.
0
๐ก Tip: D = 1 / f (metres).
How It Works
Key concepts behind this calculator
1
Enter Values
Fill in each field with your own numbers.
2
Calculate
Results update as you change the inputs.
3
Review
Read the breakdown and the explanation.
4
Adjust
Change values to compare scenarios.
Quick Reference Guide
Diopter Quick Guide
Typical values for reference.
| Focal cm | Power | Type | Type |
|---|---|---|---|
| 200 | 0.50 D | Converging | 0.50 D |
| 100 | 1.00 D | Converging | 1.00 D |
| 50 | 2.00 D | Converging | 2.00 D |
| 25 | 4.00 D | Converging | 4.00 D |
| Rule of Thumb | Check inputs | Use as a guide | Round sensibly |
Common Questions
Diopter Calculator FAQ
Answers to common questions about this calculator.
The unit of lens power, one over focal length in metres.
A diverging lens.
No, see an optician.
Thin lens powers add.