Free Online Eye Test — Vision Check in Your Browser
Calibrate your screen with a US quarter (24mm), then check your vision with a Landolt C chart at 3 m, 1 m, 20 in, or 12 in. Results shown in both decimal and Snellen (20/20) notation.
How to Use This Eye Test
This free online eye test runs entirely in your browser — no app download required. Because every phone screen is a different size, we first calibrate using a US quarter (diameter: 24.26 mm). Once calibrated, the tool displays a Landolt C (the international standard eye-test symbol) at the correct physical size for your chosen viewing distance. Choose the gap direction you can just barely make out, and your vision score is displayed in both decimal and Snellen (20/20) notation.
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STEP 1: Calibrate Your Screen
Place a US quarter (or any coin of known size) on your screen. Drag the slider until the circle matches your coin exactly.
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About the Landolt C Chart
Why a Landolt C?
The Landolt C (or Landolt ring) is the international standard for visual acuity testing, adopted by the International Council of Ophthalmology. Unlike letter charts (Snellen letters), it works equally well regardless of your native language or literacy.
Decimal vs. Snellen
European and Asian countries often use decimal notation (e.g., 1.0), while the US uses Snellen fractions (e.g., 20/20). Both mean the same thing — you can read at normal distance what a person with standard vision reads. This tool shows both.
Frequently Asked Questions
- Q. Is this eye test accurate?
- It's a reliable estimate. We calibrate the Landolt C to your exact screen size using a coin, so the symbol is displayed at its correct physical size. That said, room lighting, screen brightness, and protective film can introduce small errors. Use this as a guide, not a clinical result.
- Q. What does 20/20 vision mean?
- 20/20 (Snellen) means you can clearly read at 20 feet what a person with standard vision reads at 20 feet — it equals 1.0 in decimal notation. 20/40 means you need to be at 20 feet to see what most people see at 40 feet (decimal: 0.5).
- Q. Does this work on iPhone and Android?
- Yes. The tool runs in any modern browser — Safari on iPhone or Chrome on Android. No app installation needed.
- Q. What are the different test distances for?
- 10 ft (3 m) approximates the standard distance used in most clinical eye charts. 12 in (30 cm) checks near vision — useful for reading or phone use. Use whichever matches your daily activity.
- Q. My result seems worse than usual — what should I do?
- First, make sure your screen is at full brightness and the room is well lit. If results are still low compared to your last eye exam, schedule a visit with an optometrist. Early detection of vision changes is important.