This page gives you a true-size Snellen chart on screen, calibrated with a credit card and sized for 10, 8 or 6.5 feet, plus a printable 10 ft chart. Use it for a quick visual acuity check at the counter: do the customer’s current glasses still work, or is it time for a new exam. It does not replace a full eye exam.
Take the fitting measurements from a photoOptogrid measures PD, monocular PD and fitting height straight from the browser. No pupillometer needed.Try it freeSee the demo
Printable Snellen chart for 10 feet
Download the printable Snellen chart, US Letter, for 10 feet. Print it at 100 % (actual size), not “fit to page”, then check that the bar on the sheet measures 100 mm. If it does, the 20/200 letter measures 44.3 mm. The sheet has a QR code that opens this page, so the screen version is one scan away.
How to use the screen chart in the shop
- Calibrate once. Hold a credit or debit card to the screen and resize the box until it matches the card. The device remembers it.
- Pick the distance. 10 ft is the default; 8 ft and 6.5 ft are there for shorter rooms.
- Pick the characters. Letters, numbers, or the tumbling E, which works for children and for customers who do not read letters.
- Run the chart. Swipe down for bigger, swipe up for smaller, tap for new characters. On a keyboard, use the Up and Down arrows, Space for new characters, F to switch between line and chart view, and Esc to go back to setup.
On a phone or tablet, use landscape, put the device on a stand at the customer’s eye height, turn brightness up, and switch off dark mode and any night filter.
Why it works at 10 feet instead of 20
The classic chart is built for 20 feet. This one sizes every letter for the distance you choose, based on a 20/20 letter subtending 5 minutes of arc. At 10 ft, the 20/200 letter is 44.3 mm tall. The calibration card is a standard ISO/IEC 7810 ID-1 card, 85.60 x 53.98 mm, so once the box matches the card the letters are true size on that screen. Big lines show fewer letters on a phone, and a line that does not fit the screen is marked unavailable rather than shrunk.
Reading the result
Lines are labeled in 20/20 form, from 20/200 down to 20/15: 20/200, 20/100, 20/70, 20/50, 20/40, 20/30, 20/25, 20/20 and 20/15. A customer who gets 20/40 reads at 20 feet what a typical eye reads at 40. For what the numbers measure, see visual acuity; for where the chart comes from, see how the Snellen chart works.
The same counter is where the Optogrid app measures PD and segment height from a photo.
Frequently Asked Questions
Does the Snellen chart work on a phone?
Yes. Use landscape, a stand at the customer’s eye height, full brightness, and no dark mode or night filter. Large lines show fewer letters on a small screen, and a line that does not fit is unavailable rather than shrunk.
How do I print a Snellen chart at actual size?
Print the PDF at 100 % (actual size), not “fit to page”. Then measure the bar on the sheet: it should read 100 mm. If it does, the 20/200 letter is 44.3 mm.
What distance should I use in a small exam room?
Pick the longest distance that fits: 10 ft, 8 ft or 6.5 ft. The tool resizes every letter for that distance, so the line labels stay in 20/20 form.
What does 20/40 mean?
The customer reads at 20 feet what a typical eye reads at 40 feet.