👁️Eye Test

About this tool

First, match the blue box to the edge of a bank card held against the screen, the long edge on a computer or the short edge on a phone, so the page knows how large a millimetre is. Then enter how far you are standing from the screen, choose the eye you are testing and cover the other one. Read each line of letters and press "I can read it" to go smaller, or "Too blurry" to stop. The result is given as a Snellen fraction such as 6/6 or 20/20.

How a Snellen-style test works

Visual acuity is measured by the smallest letters you can read at a set distance. On a Snellen chart, a 6/6 (20/20) letter is 5 arcminutes tall, which is the size a person with normal vision can just read. At 3 metres that is about 4.4 mm, and a 6/60 (20/200) letter is ten times taller, about 44 mm. The calculator sizes each line from your viewing distance and the screen calibration. A bank card is used because every card is the same size, 85.6 × 54 mm. The letters are the Sloan letters used on modern charts, shown in random order so you cannot memorise them. Stand 3 metres away if you can, because at shorter distances the smallest lines become too small for a screen to draw cleanly. Wear your usual distance glasses or lenses and test each eye separately. 6/12 (20/40) is roughly the standard for driving in many countries. Honest limits: this is a screening check, not an eye examination. Lighting, glare and screen contrast affect the result, and a letter chart cannot detect conditions such as glaucoma, cataracts or macular degeneration. See an optometrist for regular eye examinations and promptly if your vision changes. Not medical advice. The colour blindness simulator shows how colours look with colour vision deficiency, the dead pixel test checks the screen and the hearing test checks your hearing range.

Frequently asked questions