Visual acuity notation converter
Convert a recorded visual acuity value among Snellen feet, Snellen meters, decimal acuity, and logMAR notation.
Select the notation shown on the record, then enter its numeric value.
Full-line reference values; individual charts and scoring systems may differ.
| Snellen feet | Snellen meters | Decimal | logMAR |
|---|---|---|---|
| 20/10 | 6/3 | 2 | -0.30 |
| 20/20 | 6/6 | 1 | 0.00 |
| 20/25 | 6/7.5 | 0.8 | 0.10 |
| 20/40 | 6/12 | 0.5 | 0.30 |
| 20/50 | 6/15 | 0.4 | 0.40 |
| 20/80 | 6/24 | 0.25 | 0.60 |
| 20/100 | 6/30 | 0.2 | 0.70 |
| 20/200 | 6/60 | 0.1 | 1.00 |
| 20/400 | 6/120 | 0.05 | 1.30 |
In 20/40 Snellen notation, 20 is the testing distance in feet and 40 is the distance at which the reference detail is designed to be resolved. The metric counterpart is 6/12. Both convert to decimal acuity 0.50 and approximately logMAR 0.30.
Mathematical conversion can produce a denominator that is not printed on a particular eye chart. The calculator therefore shows formula-based equivalents separately from the nearest common line. Real results may be scored letter by letter, and converting a Snellen record does not recreate a direct logMAR test. Keep the original notation for clinical, occupational, or licensing decisions.
A visual acuity value does not describe prescription power, peripheral vision, color vision, contrast sensitivity, eye pressure, or eye health. Results also depend on test distance, chart calibration, lighting, correction worn, and testing method. Use the notation supplied by the examining professional for medical, occupational, or licensing decisions.
These tools provide general education only. They do not diagnose an eye condition, replace a comprehensive eye exam, or provide a prescription for glasses or contact lenses.
Maintained by the AstigmatismTest.com Editorial Team. Last reviewed and updated . The team checks the method, limits, and wording against the references below; this byline does not claim review by a licensed clinician. Read our editorial policy.