What is the Feet and Inches Calculator?
This calculator lets you add or subtract two measurements given in feet and inches — a common task in construction, carpentry, sewing, and home improvement. Because feet and inches mix two units, the math is easier if you first convert each length to a single value in inches, perform the arithmetic, then convert the answer back into feet and inches.
How to use it
Enter the feet and inches for Length 1 and Length 2, choose whether to add or subtract, and submit. The result shows the answer in feet and inches, the equivalent total inches, and the value as decimal feet (handy for spreadsheets and CAD tools).
The formula explained
There are 12 inches in a foot, so a measurement is converted with $$\text{total inches} = \text{feet} \times 12 + \text{inches}$$. After adding or subtracting the two inch totals, the whole number of feet is the integer part of the result divided by 12, and the leftover is the remaining inches.
Worked example
Add 5 ft 6 in and 2 ft 9 in. Length 1 = \(5\times12 + 6 = 66\) in. Length 2 = \(2\times12 + 9 = 33\) in. Sum = 99 in. Divide by 12 → 8 ft with a remainder of \(99 - 96 = 3\) in. So the answer is 8 ft 3 in (8.25 ft).
FAQ
Can inches be a decimal? Yes — you can enter values like 6.5 inches; the calculator handles fractional inches.
What if the subtraction is negative? If Length 2 is larger, the total inches will be negative and the feet result is shown as a negative value, indicating the second length exceeds the first.
What is "decimal feet"? It is the entire measurement expressed as feet only — for example 8 ft 3 in equals 8.25 ft. This format is useful for area and material calculations.
