Visual Acuity
Visual acuity is a measure of how clearly you can see, usually expressed as a fraction like 20/20. It reflects the sharpness of your central vision — how well you can distinguish fine details, such as letters on a chart, at a given distance. The most common way to measure it is the Snellen Chart, a chart of letters that get progressively smaller with each row. A person with 20/20 vision can read a specific row from 20 feet away; someone with 20/40 vision needs to be twice as close (10 feet) to read what a person with normal vision can read from 20 feet. This test is a simple, widely used way to screen for nearsightedness, farsightedness, and other clarity issues.
For an accurate at-home screening:
- Use a credit card or ID card to calibrate your screen size accurately
- Sit at the recommended distance from your screen (10 feet is best)
- Test one eye at a time, covering the other without pressing on it
- Keep your glasses or contacts on if you normally wear them for distance vision
Keep in mind that results depend on your screen and calibration, and are intended for awareness only — not a medical diagnosis.
Visual Acuity Test
This test estimates how sharp your eyesight is using a Snellen-style chart, calibrated to your actual screen size. It takes about 3 minutes and tests each eye separately.
Step 1 · Calibrate Your Screen
Hold a credit card, ID card, or driver's license up to your screen. Drag the slider below until the box exactly matches the width of your card.
Box width: 300px
Step 2 · Set Your Distance
Sit back from your screen at the distance below, then hold your device steady (or lean your laptop against something stable).
Can you read this line clearly?
Cover your other eye and keep both eyes' focus at the same distance you set. Read the letters aloud or silently to yourself.