Quick Answer: 5 ft 5 in is 65 in. 10 feet is 120 inches, 5 ft 11 in is 71 inches, and 100 inches is 8 ft 4 in. Multiply the feet by 12 and add the inches.
What does this calculator do?
This feet to inches converter adds up feet and inches into a single number of inches, or splits a number of inches back into feet and inches. It also writes the inches as a fraction to the nearest sixteenth (or eighth, thirty-second or sixty-fourth), which is how a tape measure reads and how plans and cut lists are usually written.
The rule is simple and exact: a foot is 12 inches by definition. The questions people actually bring are messier. A height written 5'5" has to become 65 inches for a form. A laser measure reads 27.3 inches and the tape only has sixteenths. A length of 5.5 feet is not 5 feet 5 inches. The converter handles each of those, and tells you when a fraction is rounded.
It also gives the length in centimetres, since 1 inch is exactly 2.54 cm.
Using the Feet to Inches Converter
- Choose the direction. Feet and inches to inches uses the Feet and Plus inches boxes. Inches to feet and inches uses the Total inches box.
- Type the numbers. Feet can be a decimal (5.5), and inches can be a decimal too; type 3/8 as 0.375.
- Pick the fraction precision if you want a tape measure reading. Sixteenths suit most tapes.
- Read the result at the top. The cards show total inches, feet and inches, decimal feet, the inches as a fraction, and centimetres.
The preset buttons load 10 feet, 5 ft 11 in, 100 inches and a decimal reading of 27.3 inches.
How is this calculated?
- Total the inches. In feet and inches mode, the feet are converted to inches through the exact sizes of the two units (a foot is 0.3048 m and an inch 0.0254 m, a ratio of exactly 12) and the extra inches are added. In inches mode, the total is the number you typed. Negative boxes are read as zero.
total inches = feet × 12 + inches
- Split into feet and inches. The total in feet is cut at the decimal point. The whole number is the feet; the part left over is turned back into inches and rounded half up to two decimal places. If those inches round up to 12, a foot is added and the inches read 0.
feet = ⌊(total inches)/12⌋
- Write the inches as a fraction. The total inches are multiplied by the chosen denominator, rounded half up to a whole number, and written as whole inches plus a reduced fraction. A fraction that rounds up to a whole inch carries. If the rounding changed the value, the reading starts with "about".
- Convert to centimetres. The total inches are converted at exactly 2.54 cm each.
- Round for display only. Total inches are shown to four decimal places, decimal feet to six and centimetres to two.
Worked Example
The default, 5 ft 5 in to inches:
- Total inches: 5 × 12 + 5 = 65 in.
- Decimal feet: 65 ÷ 12 = 5.416667 ft.
- Centimetres: 65 × 2.54 = 165.1 cm.
10 feet: 10 × 12 = 120 in, or 304.8 cm.
5 ft 11 in: 5 × 12 + 11 = 71 in, or 180.34 cm.
Going the other way, 100 inches: 100 ÷ 12 is 8 with 4 left over, so 8 ft 4 in, which is 8.333333 ft.
A laser reading of 27.3 inches: split, it is 2 ft 3.3 in. As a fraction, 27.3 × 16 = 436.8, which rounds to 437 sixteenths, about 27 5/16 in.
Feet to Inches: Common Lengths
| Feet | Inches | Feet and inches |
|---|---|---|
| 0.25 | 3 | 0 ft 3 in |
| 0.5 | 6 | 0 ft 6 in |
| 1 | 12 | 1 ft 0 in |
| 1.5 | 18 | 1 ft 6 in |
| 2.5 | 30 | 2 ft 6 in |
| 5.5 | 66 | 5 ft 6 in |
| 6.5 | 78 | 6 ft 6 in |
| 8 | 96 | 8 ft 0 in |
| 10 | 120 | 10 ft 0 in |
| 12 | 144 | 12 ft 0 in |
| 20 | 240 | 20 ft 0 in |
Heights in Inches
| Height | Inches | Centimetres |
|---|---|---|
| 4 ft 10 in | 58 | 147.32 |
| 5 ft 0 in | 60 | 152.4 |
| 5 ft 4 in | 64 | 162.56 |
| 5 ft 5 in | 65 | 165.1 |
| 5 ft 7 in | 67 | 170.18 |
| 5 ft 10 in | 70 | 177.8 |
| 6 ft 0 in | 72 | 182.88 |
| 6 ft 2 in | 74 | 187.96 |
For heights given in centimetres, the cm to feet and inches converter is laid out for that job.
How Do You Convert Inches From Decimal to Fraction?
Multiply the decimal part by the denominator you want, round to a whole number, and put it over that denominator. For sixteenths, 0.3 × 16 = 4.8, which rounds to 5, so 0.3 inch is about 5/16 inch. Reduce the fraction if you can: 4/16 is 1/4, and 8/16 is 1/2.
The converter does this on the Total inches as a fraction card.
| Decimal inches | Nearest 1/16 inch |
|---|---|
| 0.1 | about 1/8 |
| 0.2 | about 3/16 |
| 0.3 | about 5/16 |
| 0.4 | about 3/8 |
| 0.6 | about 5/8 |
| 0.7 | about 11/16 |
| 0.8 | about 13/16 |
| 0.9 | about 7/8 |
| 3.15 | about 3 1/8 |
| 7.85 | about 7 7/8 |
What does this calculator not account for?
- Fractions typed as fractions. The boxes take decimals. Type 5 3/8 as 5.375.
- Saw kerf and tolerances. A cut list in sixteenths assumes the blade's width is allowed for separately.
- Very fine fractions. Even sixty-fourths are a rounding. For machining, work in decimal inches or millimetres.
- Survey feet. Old US land surveys used a survey foot slightly longer than the international foot, retired by NIST at the end of 2022. The foot here is 12 inches of exactly 2.54 cm.
What mistakes do people make with this?
- Reading 5.5 ft as 5 ft 5 in. It is 5 ft 6 in, because the decimal is a fraction of 12 inches. The feet to inches table shows 5.5 ft as 66 inches.
- Writing 5'5 as 5.5. 5'5" is 5 feet 5 inches, which is 5.416667 ft, not 5.5 ft.
- Rounding a fraction twice. Round once, from the full decimal. Rounding to eighths and then to sixteenths can land on a different mark.
- Forgetting the carry. 11.97 inches at sixteenths rounds to 12, which is a whole foot, not 0 ft 12 in.
Frequently Asked Questions
How many inches is 5'5"?
How many inches are in 10 feet?
How many inches is 5 ft 11 in?
How many feet is 100 inches?
How many inches are in a foot?
What is 0.3 inch as a fraction?
How do I convert 5.5 feet to inches?
Sources
- NIST Handbook 44, Appendix C, General Tables of Units of Measurement: the inch, foot and yard. nist.gov/pml/owm/nist-handbook-44-current-edition
- National Bureau of Standards Miscellaneous Publication 233, Units of Weight and Measure (revised to the 1959 refinement of the yard and the pound announced in the Federal Register, 24 FR 5348). nvlpubs.nist.gov/nistpubs/Legacy/MP/nbsmiscellaneouspub233.pdf
- NIST, The US Survey Foot: retirement of the survey foot at the end of 2022. nist.gov/pml/us-surveyfoot