There’s a doorframe in my house with decades of pencil marks on it — kids, nieces, nephews, one ambitious dog. Every mark is in feet and inches, because that’s how height works in my head and always has.
But I’ve watched visitors raised on metric squint at a mark labeled 5’10” like it was a cipher. Five point ten of what? Why two numbers? Fair questions. The notation is simple once decoded: the single quote means feet, the double quote means inches. So 5’10” is five feet, ten inches — and since a foot holds 12 inches, you’re in base-12 territory, not decimal.
The twelve will trip you up
The classic mistake is reading the inches as decimals. A height of 5’10” is not 5.10 feet — it’s 5 feet plus 10/12 of a foot, about 5.83 feet. And someone who’s 5’11” is only one inch shorter than someone who’s 6’0”, even though the numbers look like a bigger gap.
Averaging goes wrong the same way. The midpoint between 5’8” and 6’0” is 5’10”, not 5’9” — you have to work in total inches. Convert first (5’8” is 68 inches, 6’0” is 72) and the arithmetic behaves itself.
Getting to centimeters cleanly
The reliable route: convert everything to inches, then multiply by 2.54. A 5’10” person is 70 inches, and 70 times 2.54 is 177.8 cm. Some landmarks worth having on hand:
| Feet and inches | Centimeters |
|---|---|
| 5’0” | 152.4 |
| 5’6” | 167.6 |
| 5’10” | 177.8 |
| 6’0” | 182.9 |
| 6’4” | 193.0 |
Going the other direction, divide centimeters by 2.54 for total inches, then peel off the feet. Someone who’s 170 cm is 66.9 inches, which rounds to 5’7”.
Two anchors do most of the work
For everyday guessing, I keep just two numbers in my head: 5 feet is about 152 cm, and every inch after that adds roughly 2.5 cm. That’s the whole system. Hear that someone is 6’2”? That’s 5 feet plus 14 inches — 152 plus 35, call it 188 cm. The exact answer is 187.96, so the shortcut lands almost on the nose.
The reverse anchor earns its keep too: 180 cm sits a shade under 5’11”. A lot of people cluster right around there, so it comes up more than you’d think — at least it does when the topic of height breaks out at a dinner table, which in my experience it reliably does.
Whenever feet and inches stump you, convert to total inches first, and the rest is one multiplication away.
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