Diopters to focal length in millimeters
Type a value in D to get it in mm instantly.
500mm
That's about the same as reading glasses. That brings light to a focus about 500 mm away.
Convert the other way: mm to D
What it means
How strong is that lens?
Prescriptions carry a cylinder and an axis as well, for astigmatism. This page converts the sphere, which is the main number.
The math
How to convert D to mm
Power and focal length are reciprocals: diopters = 1 ÷ focal length in meters, so focal length in mm = 1000 ÷ diopters.
Example: 2 D = 500 mm.
Every unit
Your lens in every unit
Tables
D to mm conversion table
| D | mm |
|---|---|
| 0.25 D | 4,000 mm |
| 0.5 D | 2,000 mm |
| 1 D | 1,000 mm |
| 1.5 D | 666.667 mm |
| 2 D | 500 mm |
| 2.5 D | 400 mm |
| 3 D | 333.333 mm |
| 4 D | 250 mm |
| 6 D | 166.667 mm |
| 10 D | 100 mm |
| 20 D | 50 mm |
mm to D conversion table
| mm | D |
|---|---|
| 50 mm | 20 D |
| 100 mm | 10 D |
| 167 mm | 5.98802 D |
| 250 mm | 4 D |
| 333 mm | 3.003 D |
| 400 mm | 2.5 D |
| 500 mm | 2 D |
| 667 mm | 1.49925 D |
| 1,000 mm | 1 D |
| 2,000 mm | 0.5 D |
| 4,000 mm | 0.25 D |
Quick answers
Quick answers
- How many mm is 1 D?
- 1 D is 1,000 mm.
- How many mm is 10 D?
- 10 D is 100 mm.
- How many mm is 2 D?
- 2 D is 500 mm.
The units
About these units
Diopters (D)
One divided by the focal length in meters. Diopters simply add.
Focal length in millimeters (mm)
How camera and microscope lenses are labeled.
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