Eyesight numbers · 20/40 explained
What does 20/40 vision mean?
20/40 means that at 20 feet you make out what a typical eye makes out from 40 feet — detail arrives at half the usual range. It is the one chart result with a rule attached to it: 20/40 is the line most US states use for an unrestricted driver's licence. It corresponds to an approximate −0.75 glasses number, which is mild.
Your chart result
20/40
20/40 sits low in the mild band (−0.25 to −3.00) at an approximate −0.75. It is the last row before the driving line goes from cleared to missed: one step coarser is 20/50, which most states no longer accept for an unrestricted licence.
What 20/40 actually means
The halving is the thing to picture. A road sign a passenger reads from 40 feet you read from 20; a house number across a street, a bus route on the front of the bus, a name on a lecture slide all come in noticeably later. Faces stay readable across a room and go generic across a car park. Close-up is untouched — a phone at arm's length, a book, a keyboard are exactly as sharp as they are for anyone.
On the road, 20/40 is the threshold rather than a failure. Most US states issue an unrestricted licence at 20/40 or better, and the test is taken with whatever lenses you normally wear, so someone who reads 20/40 bare-eyed and 20/20 with glasses simply gets a corrective-lens condition on the licence. States that sit at 20/40 exactly tend to be strict about it, which is why this row, and not a coarser one, is the one people look up.
The approximate −0.75 band that pairs with 20/40 is a ballpark: the chart records what you resolve, the glasses number records how much lens sharpens it, and the two do not convert cleanly. And the row is a long way from “legally blind”, which means 20/200 or worse in the better eye with the strongest suitable lenses on.
See where any number lands
20/40is one point on the scale. The free interactive explainer takes any 20/xx chart result or glasses number and shows the clear distance, the mild-to-high band, and what “legally blind” does and doesn't mean — with the diagrams above and a side-by-side chart-to-glasses table.
Open the eyesight-numbers explainer →
Not sure which line is yours? The free online eye test draws a real letter chart sized for your screen and your distance and reads a 20/xx line per eye. Test your own line →
Have the paper from the optician? The free eye prescription calculator explains every number on it.
Common questions
What does 20/40 vision mean?
At 20 feet you make out what a typical eye makes out from 40 feet, so distant detail arrives at half the usual range. Signs, house numbers and faces across a car park read late; close-up vision is unaffected. It matches an approximate −0.75 glasses number.
Can you drive with 20/40 vision?
Yes — 20/40 is the line most US states use for an unrestricted licence, so it passes, though states that set the bar there apply it strictly. The test counts the vision you have with the lenses you normally wear, so glasses that bring you to 20/20 simply add a corrective-lens condition.
Is 20/40 vision bad?
It is mild — an approximate −0.75 glasses number, with close and mid-range vision untouched. What makes 20/40 worth knowing is not severity but the rule attached: it is exactly where the usual US unrestricted-licence line sits.
What glasses number is 20/40 vision?
An approximate −0.75. The chart and the glasses number measure different things, so treat it as a ballpark — two people who both read 20/40 can be written down a quarter-step apart.
What to do with your number
The full method is a structured 90-day program — proper lenses, measured progress, the things only experience can tune.
EndMyopia members work on lowering their glasses numbers step by step. The whole thing — your numbers explained, lens recommendations, daily habits, weekly check-ins — lives inside BackTo20/20. Full Program $1,788 $149/mo × 12 · lifetime access · money-back guarantee.
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Or keep exploring with the free Eyeball Analyzer (20 minutes, your numbers, what they mean).
Limitations & disclaimer
EndMyopia treats myopia as a refractive state, not a medical condition. This is a free educational tool — not medical advice, diagnosis, or a substitute for a licensed optometrist. Measurements depend on camera quality and how carefully you mark the card edges; expect ±5–10 % on laptops, ±10–15 % on phones. For lens orders, eye health concerns, or any task requiring full 20/20 vision, see a licensed professional.
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