Visual Acuity Test

Test your vision with a digital Snellen eye chart. Calibrate your screen, test each eye, and get your approximate visual acuity.

Step 1: Screen Calibration
Hold a standard credit card or ID card against the rectangle below. Drag the right edge of the box until it matches the card width exactly (85.6 mm).
Place card here
Drag right edge to fit
This helps us calculate the correct letter sizes for your screen.
Adjust width: 200px
Step 2: Position Yourself
Sit exactly 1 meter (about 3.3 feet) from your screen. If you normally wear glasses or contacts for distance, put them on now. You will test one eye at a time.
Cover your left eye with your hand. Do not press on the eyelid.
Testing Right Eye
Row 1 of 8
E
Your Results
This is NOT a replacement for a professional eye exam. Results are approximate and depend on screen calibration, viewing distance, and lighting conditions. See an optometrist or ophthalmologist for accurate vision testing.
Ad Space

Understanding Visual Acuity

Visual acuity measures the sharpness of your vision. It is typically expressed as a fraction like 20/20 (or 6/6 in metric), where the first number is your testing distance and the second number is the distance at which a person with normal vision could read the same line.

What Does 20/20 Vision Mean?

20/20 vision means you can see at 20 feet what a person with normal vision can see at 20 feet. It is considered normal visual acuity. Having 20/40 vision means you need to be at 20 feet to see what a person with normal vision sees at 40 feet, indicating reduced acuity.

The Snellen Chart

The Snellen chart was developed by Dutch ophthalmologist Herman Snellen in 1862. It uses optotypes (standardized letters) of decreasing size. The standard chart has 11 rows, with the largest letter corresponding to 20/200 and the smallest to 20/10. In clinical practice, the chart is viewed from 20 feet (6 meters).

Factors Affecting Results

Online visual acuity tests are less accurate than in-clinic exams because of variables like screen resolution, brightness, ambient lighting, and imprecise viewing distance. This test uses screen calibration to improve accuracy but cannot replace professional equipment.

When to See an Optometrist

Adults should have comprehensive eye exams every 1-2 years, or immediately if experiencing blurred vision, headaches while reading, difficulty seeing at night, or sudden vision changes. Children should have their first eye exam by age 3 and before starting school.

Common Vision Conditions

Myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia are common refractive errors that affect acuity. All are correctable with glasses, contact lenses, or refractive surgery. Early detection through regular testing leads to better outcomes.