The factor is exactly 12, and the mental-math shortcut
inches = feet × 12
One foot is defined as exactly 12 inches, so you just multiply. To do it in your head, multiply by 10 and add double the feet: 7 ft → 70 + 14 = 84 in. If you have feet and inches, convert the feet and add the rest: 5'8" = (5 × 12) + 8 = 68 in.
Quick reference
| Feet | Inches | Centimeters |
|---|---|---|
| 0.5 ft | 6 in | 15.24 cm |
| 1 ft | 12 in | 30.48 cm |
| 3 ft | 36 in | 91.44 cm |
| 5 ft | 60 in | 152.4 cm |
| 5.5 ft | 66 in | 167.64 cm |
| 6 ft | 72 in | 182.88 cm |
| 10 ft | 120 in | 304.8 cm |
| 100 ft | 1,200 in | 3,048 cm |
Height reads the same way: 5'9" is 69 in (175 cm), 6'0" is 72 in (183 cm).
Fractions of a foot, and the notation trap
- Fractional feet. Turn the fraction into a decimal and ×12: 3/4 ft = 0.75 × 12 = 9 in; 1/2 ft = 6 in; 1/4 ft = 3 in.
- 5'10" is not 5.10 ft. Ten inches is 10/12 = 0.83 of a foot, so 5'10" = 5.83 ft. The decimal point after a foot mark is a common source of wrong conversions.
- The symbols. A single prime (') marks feet and a double prime (") marks inches, so 6'2" means 6 feet 2 inches, which is 74 in.
Common questions
How many inches are in a foot?
Exactly 12. This is a definition, not a rounded value, so the answer never changes.
How do I convert feet and inches, like 5 foot 7, to inches?
Multiply the feet by 12 and add the leftover inches. For 5 foot 7 that is 5 times 12 plus 7, which is 67 inches.
Is 5 foot 10 the same as 5.10 feet?
No. 5 foot 10 means 5 and 10/12 feet, which is 5.83 feet. Typing 5.10 into a decimal-feet field gives the wrong answer.
