How to use the visual acuity calculator
Convert Snellen acuity to decimal and logMAR. Enter snellen denominator (20/x) in the field above; the decimal acuity, logmar are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- d — Snellen denominator (20/x)
Worked example
With snellen denominator (20/x) = 40, the calculator gives decimal acuity ≈ 0.5; logmar ≈ 0.30103.
Frequently asked questions
What is the formula for the visual acuity calculation?
Decimal acuity = 20 / d. logMAR = log10(d / 20). Here d is snellen denominator (20/x).
What inputs do I need for the visual acuity converter calculator?
You need snellen denominator (20/x). Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.