How to Add and Subtract Feet and Inches (With Excel)

• Tahir Abbas
• November 06, 2026

Adding lengths in feet and inches is easy when you convert to inches first. Here are the steps with examples.

Updated November 2026

The one rule you need

There are 12 inches in a foot. To add or subtract lengths in feet and inches, convert everything to inches, do the arithmetic, then convert back. The feet and inches calculator does all three steps at once.

Adding

Add 5 ft 8 in and 3 ft 6 in. In inches that is 5 x 12 + 8 = 68 and 3 x 12 + 6 = 42. The sum is 110 inches. Divide by 12: 9 with a remainder of 2, so the answer is 9 ft 2 in. You can also add feet and inches separately (8 ft and 14 in) and then carry: 14 in is 1 ft 2 in, so 9 ft 2 in.

Subtracting

Subtract 3 ft 6 in from 5 ft 8 in: 68 – 42 = 26 inches, which is 2 ft 2 in. If the inches in the first length are smaller, borrow a foot. For 5 ft 3 in minus 2 ft 9 in, convert to 63 – 33 = 30 inches, or 2 ft 6 in.

Decimal feet

Plans, spreadsheets and some tools need decimal feet. Divide inches by 12 and add the feet: 9 ft 2 in = 9 + 2/12 = 9.167 ft. Going the other way, take the decimal part and multiply by 12: 0.167 x 12 = 2 inches.

Metric

One inch is exactly 0.0254 meters. So 110 inches is 110 x 0.0254 = 2.794 m.

Excel formulas

Keep feet in column A and inches in column B. Total inches: =A2*12+B2. Back to feet and inches: feet =INT(C2/12) and inches =MOD(C2,12), using the MOD function. Decimal feet: =C2/12.

Fractions of an inch

Tape measures use fractions such as 3/8. Enter them as decimals: 3/8 = 0.375, 1/4 = 0.25, 5/8 = 0.625. For material estimates, see the rebar calculator and the tank volume calculator.

Frequently asked questions