A person with 20/40 vision sees things at 20 feet that most people who don't need vision correction can see at 40 feet. This means that they are nearsighted, but only slightly. A person with 20/40 vision may or may not need eyeglasses or contacts, and can discuss his or her options with a doctor.

Having 20/40 vision means that you have half the visual acuity of a person with "normal" 20/20 vision. Specifically, it means that you must be standing only 20 feet away to clearly see an object that a person with standard vision can see clearly from 40 feet away. Visually, this looks like a slight blurriness when looking at distant objects, such as street signs or a chalkboard in a large room. While 20/40 is generally the minimum requirement to obtain a driver's license in most US states without corrective lenses, it is classified as "subnormal" or mildly impaired. Fine details like small text or facial features at a distance will appear fuzzy. In 2026, most cases of 20/40 vision are easily corrected to 20/20 with a simple prescription for glasses or contact lenses, as it is often caused by common refractive errors like nearsightedness (myopia) or astigmatism.