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Acuity
Converter.
Convert visual acuity between Snellen (20/x and 6/x), LogMAR, decimal, and MAR — instantly, with the formulas shown and the full reference table below.
20 /
20/40
Snellen (ft)
6/12
Snellen (m)
0.30
LogMAR
0.50
Decimal
2.00′
MAR (arcmin)
MAR = denominator ÷ numerator · LogMAR = log₁₀(MAR) · decimal = numerator ÷ denominatorFull conversion table
| Snellen (ft) | Snellen (m) | LogMAR | Decimal | MAR (′) |
|---|---|---|---|---|
| 20/10 | 6/3 | -0.30 | 2.00 | 0.50 |
| 20/12.5 | 6/3.8 | -0.20 | 1.60 | 0.63 |
| 20/15 | 6/4.5 | -0.12 | 1.33 | 0.75 |
| 20/16 | 6/4.8 | -0.10 | 1.25 | 0.80 |
| 20/20 | 6/6 | 0.00 | 1.00 | 1.00 |
| 20/25 | 6/7.5 | 0.10 | 0.80 | 1.25 |
| 20/30 | 6/9 | 0.18 | 0.67 | 1.50 |
| 20/32 | 6/9.6 | 0.20 | 0.63 | 1.60 |
| 20/40 | 6/12 | 0.30 | 0.50 | 2.00 |
| 20/50 | 6/15 | 0.40 | 0.40 | 2.50 |
| 20/60 | 6/18 | 0.48 | 0.33 | 3.00 |
| 20/63 | 6/18.9 | 0.50 | 0.32 | 3.15 |
| 20/70 | 6/21 | 0.54 | 0.29 | 3.50 |
| 20/80 | 6/24 | 0.60 | 0.25 | 4.00 |
| 20/100 | 6/30 | 0.70 | 0.20 | 5.00 |
| 20/125 | 6/37.5 | 0.80 | 0.16 | 6.25 |
| 20/160 | 6/48 | 0.90 | 0.13 | 8.00 |
| 20/200 | 6/60 | 1.00 | 0.10 | 10.00 |
| 20/400 | 6/120 | 1.30 | 0.05 | 20.00 |
LogMAR runs opposite to intuition: lower is better, 0.00 is the 20/20 standard, and each 0.1 step is exactly one row of an ETDRS chart (with per-letter scoring at 0.02). Decimal notation, common in Europe and Asia, is simply the Snellen fraction evaluated. Need the physical letter sizes behind these values? See the visual acuity chart reference or print a correctly-sized chart with the free eye chart generator.
Scoring like this,
built into the lane.
Ocular Edge scores every exam in Snellen and LogMAR automatically — per letter, per eye — on calibrated charts running on any TV.