Eyewear and Vision
Visual acuity converter.
Enter an acuity in any one format (20/x feet, 6/x metres, decimal or logMAR) and see it in all of them, plus the minimum angle of resolution. Runs in your browser; nothing is sent or stored.
Your acuity
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The short answer
20/20 is the same as 6/6 (metric), 1.0 (decimal) and 0 (logMAR). 20/40 is 6/12, 0.5 and 0.30. Decimal is the Snellen fraction; logMAR = -log10(decimal).
Worked example
Start with 20/40. Decimal = 20 / 40 = 0.5. Metric = 6 / 0.5 = 6/12. logMAR = -log10(0.5) = 0.30. Minimum angle of resolution = 1 / 0.5 = 2 arc minutes. In words: a person with 20/40 vision needs to be at 20 feet to see what a person with 20/20 vision sees at 40 feet.
How it works
The Snellen fraction is test distance over the distance at which a person with normal acuity sees the same letter. Wikipedia gives 6/6 (metres) as the equivalent of 20/20 (feet), and the decimal form is simply the fraction (6/6 = 1.0, 6/12 = 0.5, 6/3 = 2.0). 6/6 corresponds to resolving 1 arc minute. logMAR is the base-10 logarithm of the minimum angle of resolution in arc minutes: 1 arc minute is logMAR 0, 2 arc minutes is 0.3 (the same as decimal 0.5, or 20/40).
So decimal = 20 / x = 6 / y; MAR = 1 / decimal; logMAR = -log10(decimal). The conversions here are exact arithmetic. Printed charts round some lines (20/125 is exact 6/37.5 but listed as 6/38 in Wikipedia's conversion table), so a chart value can differ a little from the maths.
Limits. Acuity is not a prescription, and this tool does not diagnose anything. It also does not apply any legal definition (such as driving or blindness standards), which vary by place.
Common acuity lines
| Snellen (feet) | Metric | Decimal | logMAR |
|---|---|---|---|
| 20/10 | 6/3 | 2 | -0.30 |
| 20/12.5 | 6/3.8 | 1.6 | -0.20 |
| 20/16 | 6/4.8 | 1.25 | -0.10 |
| 20/20 | 6/6 | 1 | 0.00 |
| 20/25 | 6/7.5 | 0.8 | 0.10 |
| 20/30 | 6/9 | 0.667 | 0.18 |
| 20/40 | 6/12 | 0.5 | 0.30 |
| 20/50 | 6/15 | 0.4 | 0.40 |
| 20/60 | 6/18 | 0.333 | 0.48 |
| 20/80 | 6/24 | 0.25 | 0.60 |
| 20/100 | 6/30 | 0.2 | 0.70 |
| 20/125 | 6/37.5 | 0.16 | 0.80 |
| 20/160 | 6/48 | 0.125 | 0.90 |
| 20/200 | 6/60 | 0.1 | 1.00 |
Exact arithmetic from the converter above.
Sources (opened 2026-10-08): Wikipedia, Visual acuity; Wikipedia, LogMAR chart.
FAQ
What is 20/20 in metric?
6/6. Metric charts are usually read at 6 metres, which is about 20 feet, so 20/20 and 6/6 mean the same thing.
How do I convert Snellen to decimal?
Divide the top number by the bottom number. 20/40 is 0.5 and 20/200 is 0.1. Metric works the same way: 6/12 is also 0.5.
What is logMAR?
The base-10 logarithm of the minimum angle of resolution in arc minutes. 20/20 is 0, 20/40 is 0.30, and lower is better. Some people see better than 20/20, which gives a negative number.
Is 20/20 perfect vision?
No. It is a standard reference for normal acuity at distance. Many people see better than that, and acuity says nothing about colour, depth, peripheral vision or eye health.
Why does a chart show 6/38 for 20/125?
Printed charts round some lines. The exact metric value for 20/125 is 6/37.5, and the Wikipedia conversion table lists it as 6/38.
Can this tell me if I can drive or meet a legal standard?
No. Legal standards vary and are set by the authority concerned. Ask your eye-care provider or licensing office.
Disclaimer
Not medical advice. This tool does simple arithmetic on numbers you type in. It does not replace an eye exam, a prescription or the advice of an optometrist or ophthalmologist, and it is not a way to order or change a prescription. Acuity charts are not a substitute for an eye exam.