How to Use This Tool
Almost everyone converting feet and inches is converting a height, and almost every converter online
makes you split it into two boxes first. This one reads whatever you type —
5'11", 5 ft 11 in, 5-11, 5.11 or plain
71 in — and tells you underneath exactly how it interpreted you, so a typo cannot silently
become the wrong answer.
The conversion is exact
Since the international yard and pound agreement of 1959, one inch is defined as exactly 2.54 centimetres. Not approximately. The conversion introduces no error at all, which means every disagreement you have ever seen between two documents came from rounding somewhere, not from the arithmetic.
The arithmetic is two steps: multiply the feet by twelve and add the inches to get total inches, then multiply by 2.54. Five foot eleven is 71 inches, which is 180.34 cm.
The rounding trap
This matters more than it sounds. A person who is 5'11" is 180.34 cm, and every form rounds that to 180. A person who is 180 cm converts back to 70.87 inches, which rounds to 5'11" — so far so good. But 5'10.5" is 179.07 cm, which rounds to 179, and 179 cm converts back to 70.47 inches, which rounds down to 5'10". Half an inch has disappeared.
If you need a height to survive being copied between documents — a medical record, a visa application, an equipment fitting — record the centimetres to one decimal place. One decimal is enough to recover the original inch measurement every time.
Reading the panels
The exact figure is the true conversion. The rounded figure is what almost every form will actually accept. When the two would round to a different feet-and-inches value, a note appears saying so, which is the moment worth paying attention to. Total inches is included because it is what clothing size charts, door frames and most engineering drawings use.
A note on 5.11
If you type 5.11 the converter reads it as five feet eleven inches, not five point one one
feet, because that is overwhelmingly what people mean. Five point one one feet would be 5'1.3", which is a
very different person. The line under the box always states which reading was used.
