Visual acuity converter

About this calculator

Enter a vision result in the form your report uses and see it in every other common scale, with a plain-language meaning and the ICD-11 vision impairment range that single measurement falls in.

What you need

• Your vision result and how it is written, for example 20/40, 6/12, a decimal, logMAR or ETDRS letters
• Whether it was measured with glasses or contacts, or without
• Which eye was measured

How it is calculated

Decimal acuity = top number ÷ bottom number. logMAR = log10(bottom ÷ top), and decimal = 10^(−logMAR). Snellen equivalents are 20 ÷ decimal (feet) and 6 ÷ decimal (metres). The ETDRS letter estimate is 85 + 50 × log10(Snellen fraction), which is approximate. Counting fingers, hand movements and light perception are not converted.

What the result can and cannot tell you

ICD-11 grades vision impairment from the better-seeing eye with your usual glasses or contacts. The range shown is where a single measurement falls; it is not a diagnosis. Counting fingers, hand movements and light perception are recorded descriptively and are not converted.

References

1. NEMA DICOM: Visual acuity notations and conversions
2. Gregori, Feuer and Rosenfeld: Novel method for analyzing Snellen visual acuity measurements. Retina 2010
3. ICD-11 vision impairment categories (9D90)

Related

• Glasses prescription reader
• Glasses to contact lens converter
• Reading glasses strength estimator
• Functional vision guide
• All eye calculators

For information only. These tools explain numbers and do not replace an eye examination or your eye doctor’s advice. Values you enter stay in your browser.