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Feet and Inches Calculator

Add, subtract, multiply, or divide two measurements in feet and inches — with fraction input, selectable inch precision, and instant conversions to decimal feet, total inches, and metric.

Value A
ft
in
Value B
ft
in
Applies to + and − results

What This Calculator Does

The feet and inches calculator does arithmetic on two measurements written the way carpenters, builders, and DIYers actually write them — feet and inches, with fractions. Choose an operation and it returns a clean feet-and-inches answer, rounded to the fraction of an inch you pick, plus handy conversions to decimal feet, total inches, meters, and centimeters.

It handles all four operations:

  • Addition and subtraction combine two lengths into a new length.
  • Multiplication treats the two lengths as sides of a rectangle and returns an area (ft² and in²).
  • Division compares two lengths and returns a plain number — how many times one fits into the other.

How to Use It

  1. Enter Value A — feet in the first box, inches in the second.
  2. Pick the operation: +, −, ×, or ÷.
  3. Enter Value B the same way.
  4. Choose how precisely to round the inches (1/2 down to 1/64).

The answer updates as you type — there is no button to press.

Entering Fractions

Either field accepts three formats:

You typeMeaningValue
8.5Decimal inches8½ in
1/2A simple fraction½ in
8 1/2Whole number and fraction (space)8½ in
8+1/2Whole number and fraction (plus sign)8½ in

A Worked Example

Add 5 ft 8½ in and 2 ft 3¾ in, rounded to the nearest 1/16 inch:

  • 5 ft 8½ in = 68.5 in
  • 2 ft 3¾ in = 27.75 in
  • Total = 96.25 in

Dividing 96.25 by 12 gives 8 feet with 0.25 inch left over, so the result is:

8 ft 0 1/4 in — the same as 8.0208 ft, 96.25 in, or 244.48 cm.

How the Math Works

Every measurement is first converted to a single number of inches:

Total inches = (feet × 12) + inches

Addition and subtraction work on those totals, then the answer is split back into feet and inches by dividing by 12 — the whole part is the feet, the remainder is the inches. The leftover inch fraction is rounded to the nearest 1/2, 1/4, 1/8, 1/16, 1/32, or 1/64, whichever you selected.

For multiplication, the two inch totals are multiplied to get square inches, then divided by 144 (12 × 12) to get square feet. For division, one inch total is divided by the other; because both are in inches, the units cancel and the result is unitless.

Common Feet-and-Inches Conversions

Feet & inchesDecimal feetTotal inchesCentimeters
1 ft 0 in1.000 ft12 in30.48 cm
2 ft 6 in2.500 ft30 in76.20 cm
5 ft 0 in5.000 ft60 in152.40 cm
5 ft 8 in5.667 ft68 in172.72 cm
6 ft 0 in6.000 ft72 in182.88 cm
10 ft 3 in10.250 ft123 in312.42 cm

Sources

Frequently Asked Questions

How do I add feet and inches together?

Add the feet to the feet and the inches to the inches, then carry every 12 inches over into 1 foot. For example, 5 ft 8 in + 2 ft 6 in = 7 ft 14 in, and since 14 in is 1 ft 2 in, the answer is 8 ft 2 in. This calculator does the carrying for you and also handles fractional inches.

Can I enter fractions of an inch?

Yes. Type a decimal (8.5), a simple fraction (1/2), or a mixed number (8 1/2 or 8+1/2) in either the feet or the inches field. The result is rounded to the fraction of an inch you choose — anything from 1/2 down to 1/64.

How many inches are in a foot?

There are exactly 12 inches in 1 foot. To turn a total number of inches into feet and inches, divide by 12: the whole number is the feet and the remainder is the inches. For example, 62 inches is 5 feet 2 inches, because 62 ÷ 12 = 5 remainder 2.

What happens when I multiply or divide feet and inches?

Multiplying two lengths produces an area, so the result is shown in square feet and square inches (for example, a 5 ft × 3 ft space is 15 ft²). Dividing two lengths cancels the units and gives a plain number — how many times the second length fits into the first.

How do I convert feet and inches to centimeters?

Multiply the total number of inches by 2.54. First convert the feet to inches (feet × 12) and add the loose inches, then multiply by 2.54. For example, 5 ft 8 in = 68 in, and 68 × 2.54 = 172.72 cm. The calculator shows the centimeter and meter equivalents automatically.