LogMAR Visual Acuity Calculator

The LogMAR Visual Acuity Calculator estimates LogMAR scores based on your Snellen fraction inputs. This tool helps optometrists and researchers convert standard eye chart results into a precise score used for clinical tracking. Whether you are assessing surgical outcomes, checking for legal blindness eligibility, or monitoring disease progression, this calculator provides standardized data.

Standard testing distance.
The line on the eye chart you can read.
Please enter a valid number greater than 0.

How LogMAR Score Is Calculated

LogMAR, or Logarithm of the Minimum Angle of Resolution, measures visual acuity using a consistent geometric progression. This method is the gold standard for research because it creates a linear scale where every step represents an equal change in vision quality.

logMAR = -log10(Numerator / Denominator)

Where:

  • Numerator = Test distance (e.g., 20)
  • Denominator = Letter size distance (e.g., 100)

To find your score, the tool first divides the numerator by the denominator to get a decimal acuity value. Then, it calculates the base-10 logarithm of that decimal. Finally, it applies a negative sign to the result. This ensures the scale accurately reflects vision loss, making it superior for statistical analysis.

What Your LogMAR Score Means

Your LogMAR score indicates the clarity of your vision, with 0.0 representing standard normal vision. Lower or negative numbers indicate better-than-average vision, while higher numbers suggest vision impairment.

Normal Vision: A score of 0.0 corresponds to 20/20 vision. Scores between -0.30 and 0.00 mean you can see details clearly at a distance, likely meeting requirements for driving without correction.

Mild Vision Loss: Scores between 0.10 and 0.30 (like 20/25 to 20/40) suggest slight blurriness. You may need glasses for reading small print or driving at night.

Legal Blindness: A score of 1.00 or higher generally meets the U.S. definition of legal blindness. This means you can see at 20 feet what a person with normal vision sees from 200 feet away.

Important: This score measures central vision only. It does not check peripheral (side) vision, color perception, or contrast sensitivity, which are also vital for total eye health.

Disclaimer: This calculator is for informational purposes only and is not a substitute for professional medical advice. Always consult an eye care professional for diagnosis and treatment.