Visual Acuity Calculator

Calculate your visual acuity using Snellen chart measurements and convert between different notation systems.

Testing Distance (feet)Smallest Line Read

Visual Acuity Result

20/20

Snellen Acuity

Decimal Acuity: 1.00

Normal Vision

Acuity Classification

Snellen Lines Comparison

Snellen Chart Reference

Line	Letters	Letter Size	Visual Acuity
Line 1	E	88mm	20/200
Line 2	FP	66mm	20/100
Line 3	TOZ	44mm	20/70
Line 4	LPED	35mm	20/50
Line 5	PECFD	28mm	20/40
Line 6	EDFCZP	22mm	20/30
Line 7	FELOPZD	18mm	20/25
Line 8	DEFPOTEC	14mm	20/20
Line 9	LEFODPCT	12mm	20/15
Line 10	FDPLTCEO	10mm	20/10

Understanding Visual Acuity

Visual acuity is the clarity or sharpness of vision, typically measured using a Snellen chart at a standard distance of 20 feet (6 meters). The familiar 20/20 notation means you can see at 20 feet what a person with normal vision sees at 20 feet. If you have 20/40 vision, you need to be at 20 feet to see what a normal eye sees at 40 feet. Decimal notation expresses the same ratio as a number (20/20 = 1.0, 20/40 = 0.5). LogMAR is another scale used in research and clinical trials. Legal blindness is defined as 20/200 or worse in the better eye with best correction. Visual acuity is affected by refractive errors (myopia, hyperopia, astigmatism), age-related changes, and eye diseases like cataracts, glaucoma, and macular degeneration.

Practical Example

Scenario: Testing at 20 feet, you can read down to Line 6 (20/30) clearly.

Result: Your Snellen acuity is 20/30 (decimal 0.67).

Classification: Near-normal vision. You may benefit from corrective lenses for activities like driving at night or reading distant signs.

Frequently Asked Questions

What does 20/20 vision mean?

20/20 vision means you can see clearly at 20 feet what should normally be seen at that distance. It is considered standard normal vision, not perfect vision.

What is legal blindness?

Legal blindness is defined as 20/200 or worse in the better-seeing eye with best possible correction, or a visual field of 20 degrees or less.

Can visual acuity improve naturally?

In children, some conditions can be improved with early treatment. In adults, visual acuity typically requires corrective lenses, contact lenses, or surgery to improve.

How often should I have my vision checked?

Adults 18-60 should have an eye exam every 2 years. Adults over 60 should have annual exams. Children should be screened at birth, 6 months, 3 years, and before school.

What is the difference between Snellen and LogMAR?

Snellen uses fractions (20/20) while LogMAR uses a logarithmic scale where 0.0 equals 20/20. LogMAR provides more uniform steps between lines and is preferred in research.

Disclaimer: This calculator is for informational purposes only. A comprehensive eye examination by an optometrist or ophthalmologist is necessary for accurate vision assessment.