Feet and Inches Calculator
Add and subtract lengths in feet, inches, and fractions, and get the total in feet and inches to the nearest 1/16 inch, with inches, decimal feet, and millimeters. You can mix in measurements in millimeters or meters and multiply or divide the total. To find the area of a room or wall, use the Square Footage Calculator.
- Choose US or Metric. US starts each measurement in feet and inches and shows the total in feet, inches, and fractions. Metric starts in millimeters and shows the total in millimeters.
- Enter each length in a Measurement. You can change the unit of any measurement, for example to inches for a length you measured as 154 5/8 in, or to millimeters.
- Pick + to add a measurement or − to subtract it. Use Add measurement for more lengths, up to 20. Blank measurements are left out.
- Optionally, choose Multiply by or Divide by and enter a number, for example 4 to split a board into four equal pieces.
- In US, choose how finely to round with Round to, from 1/8 in to 1/64 in.
Length fields accept whole numbers, decimals, fractions, and mixed
numbers, such as 10, 5.5, 3/8, or
5 5/8. In feet and inches, you can leave either field blank
and enter 12 inches or more, such as 0 ft and
30 in. The number to multiply or divide by takes whole
numbers and decimals, such as 3 or 1.5.
How to add and subtract feet and inches
Turn each length into inches, add and subtract the inches, then turn the total back into feet and inches:
Inches = feet × 12 + inches
Feet = whole number of (total inches ÷ 12), inches left = total inches − feet × 12
10 ft 5 in is 10 × 12 + 5 = 125 in, and 2 ft 5 5/8 in is 29 5/8 in. The sum is 154 5/8 in. 154 5/8 ÷ 12 is 12 with 10 5/8 left over, so the total is 12 ft 10 5/8 in.
Lengths in millimeters, centimeters, and meters are converted with 1 in = 25.4 mm, so 1 ft = 304.8 mm. Decimal feet are total inches ÷ 12: 154 5/8 in is 154.625 ÷ 12 = about 12.8854 ft.
If you subtract more than you add, the total is negative, such as 5 ft − 7 ft 3 1/2 in = -2 ft 3 1/2 in. The minus sign shows that the second length is longer by 2 ft 3 1/2 in.
Rounding to the nearest fraction
A tape measure is marked in 1/16 inch, so the total is rounded to the nearest 1/16 in by default. In US, Round to changes this to 1/8, 1/32, or 1/64 in. When rounding changes the total, Rounded to the nearest 1/16 in appears under it. The decimal values aren't rounded to the fraction, so you can compare them with it.
The calculator adds the exact lengths and rounds only the total, so the total can differ from adding up the rounded measurements. 1 5/32 in shows as 1 3/16 in and 2 7/32 in as 2 1/4 in, which add up to 3 7/16 in. The exact sum, 3 12/32 in, is 3 3/8 in.
Multiplying and dividing a length
The number you enter multiplies or divides the total of all the measurements:
Total = (added lengths − subtracted lengths) × number, or ÷ number
To cut a 10 ft 5 in board into four equal pieces, divide by 4: 125 in ÷ 4 = 31.25 in = 2 ft 7 1/4 in. To lay out three pieces of 2 ft 3 in end to end, multiply by 3 or add three measurements. Multiplying a length by another length gives an area, not a length, so use the Square Footage Calculator for that.
Inch fractions to decimals and millimeters
Each 1/16 inch is 0.0625 in, or about 1.6 mm. The table gives every 1/16 inch up to 1 inch:
| Fraction (in) | Decimal (in) | mm |
|---|---|---|
| 1/16 | 0.0625 | 1.6 |
| 1/8 | 0.125 | 3.2 |
| 3/16 | 0.1875 | 4.8 |
| 1/4 | 0.25 | 6.4 |
| 5/16 | 0.3125 | 7.9 |
| 3/8 | 0.375 | 9.5 |
| 7/16 | 0.4375 | 11.1 |
| 1/2 | 0.5 | 12.7 |
| 9/16 | 0.5625 | 14.3 |
| 5/8 | 0.625 | 15.9 |
| 11/16 | 0.6875 | 17.5 |
| 3/4 | 0.75 | 19.1 |
| 13/16 | 0.8125 | 20.6 |
| 7/8 | 0.875 | 22.2 |
| 15/16 | 0.9375 | 23.8 |
| 1 | 1 | 25.4 |
Examples
Adding and subtracting, then multiplying
8 ft 6 in + 3 ft 9 1/4 in − 1 ft 2 in = 102 + 45 1/4 − 14 = 133 1/4 in, or 11 ft 1 1/4 in. Three of those are 399 3/4 in, or 33 ft 3 3/4 in (10,153.7 mm).
Metric measurements
1,200 mm + 850 mm − 37.5 mm = 2,012.5 mm. That's about 79.2323 in, which rounds to 79 1/4 in, or 6 ft 7 1/4 in.
Mixing feet and millimeters
6 ft + 150 mm is 1,828.8 + 150 = 1,978.8 mm, or about 77.9055 in. To the nearest 1/16 in, that's 6 ft 5 7/8 in.
FAQ
Add the feet and the inches separately, then carry every 12 inches over to a foot. 10 ft 5 in + 2 ft 5 5/8 in is 12 ft 10 5/8 in. If the inches add up to 12 or more, such as 7 in + 8 in = 15 in, carry 1 ft and keep 3 in.
Divide by 12. The whole number is the feet and the remainder is the inches: 154 5/8 in ÷ 12 is 12 with 10 5/8 left, so 12 ft 10 5/8 in. Enter the inches as one measurement in inches to see it.
0.625 in. Divide the top number by the bottom number: 5 ÷ 8 = 0.625. The table above lists every 1/16 inch as a decimal and in millimeters.
Turn the length into inches and multiply by 25.4. 6 ft 7 1/4 in is 79 1/4 in, and 79.25 × 25.4 = 2,012.95 mm, or about 2,013.0 mm.
Feet times feet is square feet, an area. This calculator multiplies a length only by a number. For the area of a room or wall, use the Square Footage Calculator.
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