Online Eye Test Chart
Check how sharp your distance vision is with a screen-calibrated eye chart. Match the outline to a bank card so the symbols are drawn at true size, enter how far you sit from the screen, then read Snellen letters or tumbling Es one line at a time. It is a quick screening, not a substitute for an eye exam.
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Not a medical test. This chart is for curiosity and screening only. It cannot diagnose eye conditions or replace an exam by an optometrist or ophthalmologist.
1 Calibrate your screen
Hold a bank card, debit card or driver's license (standard ID-1 size, 85.6 × 54 mm) flat against the screen inside the outline. Move the slider until the outline is exactly as wide as the card.
2 Set up the test
3 Read the chart
Count a line as read if you get more than half of its symbols right (for example 3 of 5). Keys: Enter = read, N = couldn't read, Space = shuffle.
Your results
Finish the line-by-line test to see your result.
| Eye | Chart | Distance | Snellen (ft) | Metric | Decimal | LogMAR |
|---|---|---|---|---|---|---|
| No results yet | ||||||
A result below 20/40 (6/12) in either eye, a difference of two or more lines between eyes, or any sudden change in vision is a good reason to book a professional eye exam.
How to use the Online Eye Test Chart
- Calibrate the screen: hold a bank card against the outline and move the slider until the widths match, then press Save calibration.
- Set the distance you will sit from the screen (10 ft or 3 m works in most rooms) and choose letters or tumbling E.
- Cover one eye, select which eye you are testing, and keep your glasses or contacts on if you normally wear them for distance.
- Read each line from your seat; press Read it correctly if you got more than half the symbols right, or Couldn't read it to finish.
- Repeat for the other eye and compare the results table. See an eye care professional if a result is worse than 20/40 or the eyes differ.
How the letter sizes are calculated
A 20/20 (6/6) optotype is drawn so that its full height subtends 5 minutes of arc at the eye, with strokes and gaps of 1 minute of arc. For a viewing distance d the letter height is:
h = d × tan(5′) × (Snellen denominator ÷ 20) ≈ d × 0.0014544 × (D ÷ 20)
At 6 m (20 ft) a 20/20 letter is 8.73 mm tall; at 3 m (10 ft) it is 4.36 mm. The page converts millimeters to screen pixels using your card calibration: pixels per mm = card outline width in pixels ÷ 85.6.
| Snellen (ft) | Metric | Decimal | LogMAR | Letter height at 10 ft / 3.05 m | Letter height at 20 ft / 6.1 m |
|---|---|---|---|---|---|
| 20/200 | 6/60 | 0.1 | 1.00 | 44.3 mm | 88.7 mm |
| 20/100 | 6/30 | 0.2 | 0.70 | 22.2 mm | 44.3 mm |
| 20/70 | 6/21 | 0.29 | 0.54 | 15.5 mm | 31.0 mm |
| 20/50 | 6/15 | 0.4 | 0.40 | 11.1 mm | 22.2 mm |
| 20/40 | 6/12 | 0.5 | 0.30 | 8.9 mm | 17.7 mm |
| 20/30 | 6/9 | 0.67 | 0.18 | 6.6 mm | 13.3 mm |
| 20/25 | 6/7.5 | 0.8 | 0.10 | 5.5 mm | 11.1 mm |
| 20/20 | 6/6 | 1.0 | 0.00 | 4.4 mm | 8.9 mm |
| 20/15 | 6/4.5 | 1.33 | −0.12 | 3.3 mm | 6.6 mm |
| 20/10 | 6/3 | 2.0 | −0.30 | 2.2 mm | 4.4 mm |
LogMAR is log₁₀ of the minimum angle of resolution in minutes of arc (D ÷ 20), so lower is better and 0.00 equals 20/20. Each line on standard charts is roughly a 0.1 logMAR step.
Getting a fair result at home
- Measure the distance with a tape measure from your eyes to the screen; guessing by a foot at 10 ft changes the result by 10%.
- Light the room evenly, set the screen to full brightness and avoid reflections from windows behind you.
- Cover one eye with your palm without pressing on it, and test each eye separately, then both together.
- Wear your distance glasses or contacts if you have them; the test then checks your corrected vision.
- Don't squint or lean forward, and use Shuffle letters if you think you remembered a line.
- Ask a helper to tick Show answers and judge each line, so you are not tempted to walk up to the screen.
When to see an eye care professional
This chart only measures one thing: how small a high-contrast symbol you can recognize at a distance. Book an exam if either eye reads worse than 20/40, if the two eyes differ by two lines or more, or if you notice blurred, double or distorted vision, flashes, floaters, a curtain over your vision, or eye pain. Sudden vision changes need urgent care. Children should have their eyes checked by a professional even if they seem to see well.
Frequently asked questions
Is an online eye test accurate?
When the screen is calibrated and you sit at the exact distance you entered, the symbols are drawn at the same angular size as a printed chart, so the result is a reasonable estimate of your distance visual acuity. Lighting, screen glare, guessing and pixel limits on small lines add error, and the test cannot check eye health, focusing, color, eye pressure or the back of the eye. Use it for screening only and see an optometrist for an actual exam.
What does 20/20 vision mean?
It means you can read at 20 feet a letter that a person with standard vision can read at 20 feet. 20/40 means you need to be at 20 feet to read what a standard eye reads at 40 feet. In metric notation 20/20 is 6/6, and as a decimal it is 1.0. A 20/20 letter is sized so that the whole letter spans 5 minutes of arc at your eye.
Why do I need to calibrate with a card?
Screens differ widely in pixel density, so the same number of pixels can be 6 mm on one screen and 10 mm on another. Bank cards, debit cards and most driver's licenses share the ISO/IEC 7810 ID-1 size of 85.60 × 53.98 mm, which makes them a convenient ruler for the on-screen outline. Without calibration the result can be off by several lines.
How far should I sit from the screen?
Classic charts are read at 20 feet (6 m). This chart recalculates the symbol sizes for any distance, but the smallest lines need enough screen pixels: at 10 ft (3 m) most laptops and monitors can draw down to about 20/15. At very short distances the bottom lines become too few pixels to be accurate and the tool warns you.
What is the tumbling E chart for?
It tests the same acuity without needing to read letters. Each E points right, left, up or down and you say, or point to, the direction its bars point. It is used for young children and people unfamiliar with the Latin alphabet.
What vision do I need to drive?
Many US states and many other countries require about 20/40 (6/12) with both eyes, with glasses if needed, for an unrestricted license, but the rules vary by state and country and often include field-of-vision requirements. Only an official vision screening counts for licensing.
Can I test with a mirror?
Yes. If your room is too small, sit beside the screen facing a mirror, tick Viewing in a mirror so the symbols are reversed, and enter the total distance: from your eyes to the mirror plus from the mirror to the screen.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.