Add, subtract, multiply or divide lengths written in feet, inches and fractions, the way they read on a tape measure. Results come back rounded to the nearest 1/16" (or the precision you choose) plus decimal feet, inches and metric.
Last updated:
Length A
Whole, decimal or fraction: 7, 7.375, 3/8, 7 3/8 or 7-3/8.
Operation
Divide by
Length B
Multiply or divide length A by this number.
Enter your values to see the result.
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How to use the Feet and Inches Calculator
Enter length A in feet and inches; inches can include a fraction like 7 3/8.
Choose the operation: add, subtract, multiply or divide.
Enter length B (for add, subtract or divide by a length) or a plain number (to multiply or split into equal parts).
Pick the precision: 1/16" matches most tape measures.
Press Calculate and read the result in feet-inches, decimal feet, inches and metric.
How feet and inches math works
Feet-inch lengths mix two units (12 inches = 1 foot) and often a fraction, so the reliable way to do math with them is to convert everything to inches first:
Convert to inches: inches = feet × 12 + inches (with the fraction as a decimal, e.g. 3/8 = 0.375).
Do the operation on the inch values.
Convert back: feet = whole part of (inches ÷ 12); the remainder is the inches.
Round the remainder to the nearest 1/16" (or the tape mark you use) and reduce the fraction (8/16 = 1/2).
Example: 5' 7 3/8" + 2' 9 15/16" → 67.375 in + 33.9375 in = 101.3125 in → 101.3125 ÷ 12 = 8 ft remainder 5.3125 in → 8' 5 5/16".
Inch fractions to decimals
Fraction
Decimal in
mm
Fraction
Decimal in
mm
1/16"
0.0625
1.59
9/16"
0.5625
14.29
1/8"
0.125
3.18
5/8"
0.625
15.88
3/16"
0.1875
4.76
11/16"
0.6875
17.46
1/4"
0.25
6.35
3/4"
0.75
19.05
5/16"
0.3125
7.94
13/16"
0.8125
20.64
3/8"
0.375
9.53
7/8"
0.875
22.23
7/16"
0.4375
11.11
15/16"
0.9375
23.81
1/2"
0.5
12.70
1"
1.0
25.40
Inches to decimal feet
Inches
Feet
Inches
Feet
Inches
Feet
1"
0.0833
5"
0.4167
9"
0.75
2"
0.1667
6"
0.5
10"
0.8333
3"
0.25
7"
0.5833
11"
0.9167
4"
0.3333
8"
0.6667
12"
1.0
Tips for measuring and cutting
Account for the saw kerf. A typical circular-saw blade removes about 1/8" per cut. When dividing a board into pieces, subtract kerf × (pieces − 1) from the length first.
Use "how many fit" (divide by a length) for stud, joist or baluster spacing: it gives the whole count and the leftover.
Measure twice, mark once: round to the same precision you can actually read on your tape; 1/16" is standard for carpentry, 1/32" for fine woodworking.
Frequently asked questions
How do you add feet and inches?
Convert both lengths to inches (feet × 12 + inches), add them, then convert back: divide by 12 for the feet and keep the remainder as inches. For example 5' 7 3/8" + 2' 9 15/16" = 67.375 + 33.9375 = 101.3125 in = 8' 5 5/16".
How do you subtract feet and inches?
Convert both lengths to inches, subtract, and convert the answer back to feet and inches. 8' − 3' 4 1/2" = 96 − 40.5 = 55.5 in = 4' 7 1/2". If the second length is longer, the result is negative.
How do I convert feet and inches to decimal feet?
Divide the inches by 12 and add the feet. 5' 6" = 5 + 6 ÷ 12 = 5.5 ft, and 7' 3 3/4" = 7 + 3.75 ÷ 12 = 7.3125 ft.
How do I divide a length into equal parts?
Choose Divide, then "A number", and enter how many parts you need. 12' 5" (149 in) split into 3 equal parts is 49.667 in each, which rounds to 4' 1 11/16" on a 1/16" tape.
What does 1/16 inch precision mean?
The result is rounded to the nearest sixteenth of an inch, the smallest mark on most tape measures. The rounding error is never more than 1/32" (about 0.8 mm), and the calculator shows the exact difference.
Can I enter metric lengths?
Inputs are in feet and inches, but every result is also shown in meters, centimeters and millimeters, so you can convert a feet-inch result to metric in one step.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.