Snellen 20/x denominators to LogMAR values Converter
Convert Snellen 20/x denominators to logMAR values using logMAR = log10(Snellen denominator ÷ 20). The formula is logMAR = log10(Snellen denominator ÷ 20); 1 20/x is -1.301 logMAR.
The denominator from a 20-foot Snellen visual acuity fraction, such as 40 in 20/40.
The base-10 logarithm of MAR, often used in vision research and chart scoring.
Start with your value in Snellen 20/x denominators, then apply the formula below. It stays visible so you can catch rounding mistakes instead of just copying the output.
Use these values for notation comparison and documentation checks only. They do not diagnose vision problems or replace an eye exam.
Visual acuity notation is often rounded to chart lines, so the converted numeric value may be more precise than the original measurement. This page displays converted values with up to 3 decimal places by default.
| Snellen 20/x denominators | LogMAR values |
|---|---|
| 10 20/x | -0.301 logMAR |
| 15 20/x | -0.125 logMAR |
| 20 20/x | 0 logMAR |
| 25 20/x | 0.097 logMAR |
| 40 20/x | 0.301 logMAR |
| 80 20/x | 0.602 logMAR |
| 200 20/x | 1 logMAR |
Useful for comparing eye chart notation systems. Use the same formula with your exact input if the measurement needs to be documented.
Useful for translating research tables and clinical references. Use the same formula with your exact input if the measurement needs to be documented.
Useful for checking educational vision examples. Use the same formula with your exact input if the measurement needs to be documented.
How do I convert Snellen 20/x denominators to logMAR values?
Enter the value in Snellen 20/x denominators and apply logMAR = log10(Snellen denominator ÷ 20). Round the logMAR values result after the conversion, not before.
What is 1 Snellen 20/x denominator in logMAR values?
1 20/x equals -1.301 logMAR with the current rounding setting. Keep more decimal places when the result feeds another calculation.
What is 10 20/x in logMAR?
10 20/x is -0.301 logMAR. It appears in the lookup table so you can compare it with nearby amounts.
Can I convert logMAR values back to Snellen 20/x denominators?
Yes. Use the reverse LogMAR values to Snellen 20/x denominators converter if you need to go the other direction.
How accurate is this Snellen 20/x denominators to logMAR values conversion?
The calculator runs the formula in your browser and rounds results to 3 decimal places by default. Visual acuity notation is often rounded to chart lines, so the converted numeric value may be more precise than the original measurement.