Vision Science Research Group

Snellen fraction conversion

    Snellen fraction conversion

    Sometimes visual acuity is recorded in other notations e.g. logMAR or cycles per degree. These other notations can (with care) be converted to a Snellen fraction for comparison. This web page will deal only with acuities recorded in Snellen fractions.

    If acuity has been recorded using logMAR or cycles per degree the tables below can be used to approximate the Snellen fraction. Also available in the tables is a conversion from metric (UK standard) to Imperial (US standard) recording.

    NOTE: tests which use logMAR or cycles per degree to record acuity may not be measuring the same type of visual acuity as a Snellen test and conversions must be treated with caution.

    Snellen equivalent LogMAR Cycles per degree (cpd)
    6/12 (20/40) 0.3 15.0
    6/18 (20/60) 0.5 10.0
    6/24 (20/80) 0.6 7.5
    6/36 (20/120) 0.8 5.0
    6/48 (20/160) 0.9 3.75
    6/60 (20/200) 1.0 3.0
    6/72 (20/240) 1.1 2.5
    6/90 (20/300) 1.2 2.0
    6/120 (20/400) 1.3 1.5
    6/150 (20/500) 1.4 1.2
    6/180 (20/600) 1.5 1.0
    6/240 (20/800) 1.6 0.75
    6/360 (20/1200) 1.8 0.50
    6/480 (20/1600) 1.9 0.28