Human eyesight is usually measured with the “20/20” scale, but that is not actually the best vision a person can have. The very best unaided human visual acuity is generally around 20/10, and some experts consider this the practical upper limit for normal human eyes.
Visual acuity numbers
Visual acuity expresses how clearly you can see detail at a distance, using a fraction such as 20/20 or 20/10.
- 20/20 means you can see at 20 feet what an average person is expected to see at 20 feet; this is considered “normal,” not “perfect.”
- 20/10 means you can see at 20 feet what an average person would need to be 10 feet away to see, so your distance vision is about twice as sharp as normal.
“Best” realistic human vision
Most eye-care sources describe 20/10 as about the best visual acuity humans reach without magnifying devices.
- Some reports mention slightly better values in rare individuals, but these are exceptional and not a typical or reliable goal.
- For everyday life, anything around 20/20 to 20/15 is already excellent vision, and 20/10 is considered extremely sharp.
Beyond just sharpness
“Best vision” is not only about the smallest letters you can read on a chart.
- High‑quality vision also depends on good depth perception, peripheral vision, contrast sensitivity, color vision, and healthy eyes overall.
- Someone with 20/10 acuity but poor contrast sensitivity or serious eye disease may function worse than a person with 20/20 acuity and otherwise healthy visual function.
