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Visual Acuity Conversion (Snellen ↔ LogMAR)

Converts between Snellen fraction and LogMAR notation — LogMAR is preferred for research/statistical analysis because it has equal-sized steps across the acuity range.

For healthcare professionals.These calculate a score or a measurement from values you enter. They do not diagnose, and they are no substitute for clinical judgement. If you are a patient, discuss any result with your own doctor rather than acting on it.

Convert From

Snellen Numerator (testing distance)

Snellen Denominator

LogMAR Value

Enter the values above to see the result.

Source

Bailey IL, Lovie JE. New design principles for visual acuity letter charts. Am J Optom Physiol Opt. 1976;53(11):740-745.

Shown for reference and checked against the source above. Confirm against current guidance before acting on it, and use your own clinical judgement.

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