Visual Acuity Test — Free Online Snellen Eye Chart Test
This online visual acuity test estimates the sharpness of your distance vision on the Snellen scale (6/6, 6/9, 6/12…). Calibrate letter size with a bank card, move about 1 metre from the screen, and pick the letters you see.
Hold any bank/ID card against the screen and drag the slider until the box matches its width, so letter sizes are accurate.
Then step back until your eyes are about 1 metre from the screen. Test one eye at a time by covering the other. Keep glasses on if you normally wear them.
What 6/6 (20/20) vision means
6/6 vision — 20/20 in feet — means your eye resolves detail at 6 metres that a standard eye resolves at 6 metres; it's the definition of normal sharpness, not "perfect" vision. On the Snellen scale, each chart line corresponds to a letter size whose strokes span a fixed visual angle: read the 6/6 line and you're normal; stop at 6/12 and you see at 6 metres what a standard eye sees from 12.
How this online eye chart works
A physical Snellen chart hangs 6 metres away; a screen can sit at 1 metre, so we scale the letters down by the same ratio — that's why calibration matters. After you match the on-screen box to a real card (all bank cards are 85.6 mm wide), the test knows your screen's true pixel size and can draw each acuity line at the correct physical height for a 1-metre distance. You'll see two letters per line; get both right to move to a smaller line.
Interpreting your result
6/6 or better: normal distance sharpness. 6/9–6/12: mildly reduced — common with small uncorrected refractive errors or a smudged screen. 6/18 or worse on a properly calibrated screen is worth a professional exam. For children, the same chart logic applies but young kids do better with picture or tumbling-E charts and should be tested by a professional. Phone screens work, but a laptop or monitor at a measured 1 metre is more reliable than a phone at arm's length.
Frequently asked questions
What is a normal visual acuity test result?
Normal visual acuity is 6/6 (the metric equivalent of 20/20): you read at 6 metres what a person with standard vision reads at 6 metres. Many young adults score slightly better, such as 6/5.
What is the meaning of 6/6 and 6/9 vision?
6/6 means you see at 6 metres what a standard eye sees at 6 metres — normal sharpness. 6/9 means you need to be at 6 metres to read what a standard eye can read from 9 metres, i.e. slightly reduced acuity.
What are visual acuity tests used for?
Visual acuity tests measure the sharpness of your distance vision. They are used in routine eye exams, driving-license screening, school checks and to track whether glasses or contact lens prescriptions need updating.
What are the 4 components of visual acuity?
Clinically, visual acuity depends on four things: the eye’s optics (focus), the health of the retina, the neural pathway to the brain, and the brain’s interpretation. A problem in any one of them lowers measured acuity.
Can I trust an online visual acuity test as much as an eye doctor’s exam?
No. An online eye chart test is a rough screening: screen size, resolution, brightness and your measured distance all introduce error, and it cannot check eye health at all. Use it to spot changes, then confirm anything unusual with an optometrist.
How is the Snellen chart used to measure visual acuity?
A Snellen chart shows rows of letters that shrink line by line, each sized so its details span a set visual angle at the test distance. The smallest line you can read reliably gives your score, e.g. 6/6 or 6/12.
How this test works: everything runs and is timed locally in your browser, and results depend on your device and conditions. Scores are for casual benchmarking and entertainment — not a clinical, medical or diagnostic measurement.