Using an Amsler grid on a phone or computer
A screen works as well as paper if two things are right: the size of the squares and the distance from your eyes.
Updated November 13, 2026 · General information, not medical advice.
The problem with grids on screens
A picture of an Amsler grid on a web page is shown at whatever size your screen makes it. On one phone it may be 5 cm across, on a monitor 25 cm. The standard grid is 10 cm with 5 mm squares, read from 12 to 14 inches (30 to 35 cm). A grid at the wrong size checks the wrong area of vision, and results from different devices cannot be compared. This is why some eye organizations tell people to print the grid.
How this site fixes the size
The online test asks you to hold a bank card against the screen and match an outline to it. Every bank card in the world is 85.6 mm wide, so one match tells the page exactly how large a millimeter is on your screen. The grid is then drawn with true 5 mm squares. The setting is remembered on that device.
Phone, tablet or computer?
| Device | Grid shown | Good for |
|---|---|---|
| Phone | About 12 to 14 squares across | A quick daily check of the very center |
| Tablet | The full 20 squares | The full test, easy to hold at reading distance |
| Laptop or desktop | The full 20 squares | The full test, if you sit 12 to 14 inches (30 to 35 cm) from the screen |
A phone held upright is narrower than 10 cm, so the test shows fewer squares at the correct size. The squares it shows are the central ones, which matter most, but changes farther out will be missed. Use a larger screen or a printed grid for the full check.
Tips for testing on a screen
- Turn the brightness up and avoid reflections.
- Clean the screen. A smear can look like a blurry patch.
- Measure the distance the first time. At a computer most people sit too far back, so lean in to 12 to 14 inches (30 to 35 cm).
- Wear the glasses you use at that distance. For most people that means reading glasses.
- Rest the device on a table or stand so it does not shake.
- Turn off night mode or color filters that dim the screen.
Doing the Amsler grid test at home
The method is the same on any device or on paper: one eye covered, the other on the center dot, noticing the lines without looking around. The full steps are in how to use an Amsler grid.
Apps and home devices
There are also phone apps and home devices that an eye doctor can prescribe for monitoring macular degeneration. Some send results to the clinic. Ask your doctor whether one suits you. They are compared in how accurate is the Amsler grid?