Feet and Inches Calculator
Add, subtract, multiply or divide lengths written in feet, inches and fractions, with the answer read to the nearest sixteenth of an inch.
Result
8 ft 2 1/8 in
To the nearest 1/16 inAnswers are exact and shown to the nearest sixteenth of an inch.
- In inches
- 98.125 in
- In feet
- 8.1771 ft
- In metric
- 2,492.4 mm (2.5 m)
https://calcgallery.com/lumber-carpentry/feet-and-inches-calculator/
Results are estimates for planning only. Actual needs vary with site conditions, products and workmanship. Always confirm quantities with your supplier and follow local building codes and manufacturer instructions. Read the full disclaimer
How to use the Feet and Inches Calculator
- Type the first length the way your tape reads it, for example 5' 3 3/8" or 5 ft 3 3/8 in. A number on its own is inches.
- Choose add, subtract, multiply, divide by a number, or divide by a length.
- Type the second length, or the number to multiply or divide by.
- Read the answer in feet, inches and sixteenths, with the same length in decimal inches, decimal feet and millimetres.
How it is calculated
Each length is converted to one number before any arithmetic, so feet, inches and fractions never have to be carried by hand:
length = feet × 12 + inches + fraction (in inches)add a + bsubtract a − bmultiply a × ndivide a ÷ nratio a ÷ bThe result is then split back into whole feet, whole inches and sixteenths. Rounding happens once, at that last step: 11 31/32 inches reads as 1 foot, not 11 16/16 inches.
Reading the answer on a tape
Most tapes are marked in sixteenths, so an answer such as 1 ft 9 1/8 in can be found directly. When a length is divided into parts, as when spacing shelves or balusters evenly, the sixteenths reading can differ from the exact share by up to 1/32 inch. Mark from one end with the running total, not by stepping the rounded part over and over, so the small errors do not add up along the run.
Metric lengths are shown alongside for checking material sold in millimetres. The inch is exactly 25.4 mm, so the conversion is exact.
With your numbers
- 5 ft 3 3/8 in + 2 ft 10 3/4 in = 8 ft 2 1/8 in
Quick reference
Answers are exact and shown to the nearest sixteenth of an inch.
| Job | Result |
|---|---|
| 5' 3 3/8" plus 2' 10 3/4" | Answer: 8 ft 2 1/8 in |
| 5' 3 3/8" minus 2' 10 3/4" | Answer: 2 ft 4 5/8 in |
| 5' 3 3/8" times 3 | Answer: 15 ft 10 1/8 in |
| 8' split in 3 | Answer: 2 ft 8 in |
| How many 16" in 12' 6" | Times the second length fits: 9.375 |
| 10' 7 5/16" times 3 | Answer: 31 ft 9 15/16 in |
Common questions about the Feet and Inches Calculator
- How do I type a fraction of an inch?
- Write it as numerator, slash, denominator: 3/8. A whole number and a fraction are separated by a space or a hyphen, so 3 3/8 and 3-3/8 both mean three and three eighths. Feet take an apostrophe or ft, inches a double quote or in, and 5'-3" in architectural style works too.
- Does 63 mean 63 inches or 63 feet?
- Inches. A number with no mark is read as inches, because that is how most cuts are measured. For feet, add the mark: 63' or 63 ft.
- How is the answer rounded?
- The arithmetic is exact. Only the feet-and-inches reading is rounded, to the nearest sixteenth of an inch, and a result that rounds up to 12 inches carries into the next foot. The decimal inch and millimetre results keep more precision if you need it.
- Can the answer be negative?
- Yes, when you subtract a longer length from a shorter one. The minus sign is shown once, in front of the whole reading.
- How many 16 inch spaces fit in a wall?
- Choose divide by a length, type the wall length first and 16 second. The answer is how many times 16 inches fits, as a decimal; a stud layout needs one more position than the whole spaces, which the framing calculator counts for you.