Convert Snellen visual acuity to LogMAR, decimal, and MAR. Check driving eligibility and compare vision classification across international standards.
The 20/20 Vision Calculator converts your Snellen visual acuity readings into multiple clinical formats including LogMAR, decimal acuity, and Minimum Angle of Resolution (MAR). Whether you've just had an eye exam or want to understand what your prescription numbers mean, this tool provides a comprehensive picture of your visual acuity status.
Visual acuity is the most fundamental measure of eye function. The Snellen fraction (e.g., 20/20) describes how well you can resolve fine detail at a standard distance. The numerator is your test distance in feet, and the denominator indicates the distance at which a person with normal vision could read the same line. So 20/40 means you must be at 20 feet to read what a normal eye reads at 40 feet.
This calculator also compares your results against international driving requirements, legal blindness thresholds, and age-expected norms. It supports both corrected and uncorrected measurements, letting you evaluate each eye independently and as a binocular pair. Use the presets to explore common clinical scenarios or enter your own values from a recent eye exam report.
Understanding your visual acuity in multiple formats helps you communicate with eye care providers, assess driving eligibility, and track changes over time. This calculator bridges the gap between the Snellen chart in your doctor's office and the clinical metrics used in research and international standards. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain.
LogMAR = log₁₀(Snellen denominator / 20) Decimal Acuity = 20 / Snellen denominator MAR = Snellen denominator / 20 (arcmin) Corrected Snellen at distance d: 20/(denom × 20/d)
Result: Right: LogMAR 0.10, Left: LogMAR 0.18 — Near Normal vision, meets driving requirement
Both eyes are slightly below 20/20 but well within the 20/40 US driving threshold. At age 45, this is within normal range.
Visual acuity is typically the first test performed in any eye examination. The Snellen chart, invented by Dutch ophthalmologist Herman Snellen in 1862, remains the gold standard despite being over 160 years old. Modern eye care uses multiple notation systems including Snellen, LogMAR (Bailey-Lovie), decimal, and metric (MAR), each with advantages for different clinical and research contexts.
While this calculator helps interpret your numbers, certain findings warrant prompt professional attention. A sudden drop in acuity in one eye could indicate retinal detachment, macular degeneration, or vascular occlusion. A difference of three or more lines between eyes (anisometropia) may affect binocular function. Any acuity below 20/40 that hasn't been evaluated should prompt an eye exam, especially for drivers.
Mild refractive errors (20/25 to 20/40) are typically correctable with glasses, contacts, or refractive surgery. Moderate errors (20/50 to 20/80) usually respond well to correction but may indicate underlying conditions. Severe low vision (20/100+) often requires specialized low-vision aids, magnification devices, and rehabilitation services beyond standard correction.
20/20 means you can see at 20 feet what a person with normal vision sees at 20 feet. It is the baseline for "normal" acuity but not perfect — some people achieve 20/15 or even 20/10.
No. 20/20 is the standard baseline. Many people, especially younger individuals, can see 20/15 or 20/10. "Perfect" vision also requires good contrast sensitivity, color vision, and peripheral vision.
LogMAR (Logarithm of the Minimum Angle of Resolution) provides a linear scale for statistical analysis. A LogMAR of 0 equals 20/20; negative values are better than 20/20; positive values are worse.
Most US states require 20/40 or better in at least one eye, with or without correction. Some states allow 20/50 or 20/60 with restrictions like daylight-only driving.
In the US, legal blindness is defined as best-corrected visual acuity of 20/200 or worse in the better eye, or a visual field of 20 degrees or less. Use this as a practical reminder before finalizing the result.
Age-related acuity decline (presbyopia) typically begins around age 40 for near vision. Distance acuity may decline after age 60, with 20/25 to 20/30 being common in healthy older adults.
Snellen uses 20 feet (US) while metric uses 6 meters. 20/20 equals 6/6. To convert, divide both numbers by 3.28 (feet to meters).