Feet and inches calculator with fractions
Enter each length as feet, inches and a fraction, pick the operation and read the answer in feet and inches rounded to the nearest 1/16 inch. 5 ft 7 1/2 in plus 6 ft 8 3/4 in is 12 ft 4 1/4 in.
Inputs used by this calculator
Feet and Inches Calculator uses the fields below. The starting values reproduce the page example; replace them with values from the same units and time period before using the result.
| Input | Starting example | Accepted value | How it is used |
|---|---|---|---|
| Operation | Add two lengths | Add two lengths · Subtract the second length · Multiply by a number · Divide by a number | Supplies the operation quantity used by the published equation or result breakdown. |
| First length (ft) | 5 | 0 to 1000000 | Supplies the first length (ft) quantity used by the published equation or result breakdown. |
| First length (in) | 7 | 0 to 1000000 | Supplies the first length (in) quantity used by the published equation or result breakdown. |
| First length, fraction of an inch | 1/2 | 0 · 1/16 · 1/8 · 13 more choices | Supplies the first length, fraction of an inch quantity used by the published equation or result breakdown. |
| Second length (ft) | 6 | 0 to 1000000 | Supplies the second length (ft) quantity used by the published equation or result breakdown. |
| Second length (in) | 8 | 0 to 1000000 | Supplies the second length (in) quantity used by the published equation or result breakdown. |
| Second length, fraction of an inch | 3/4 | 0 · 1/16 · 1/8 · 13 more choices | Supplies the second length, fraction of an inch quantity used by the published equation or result breakdown. |
| Multiply or divide by | 3 | 0 to 1000000 | Selects the unit or conversion path used by Feet and Inches Calculator. |
| Round to the nearest | 1/16 inch | 1/16 inch · 1/8 inch · 1/4 inch · 1/32 inch | Selects the unit or conversion path used by Feet and Inches Calculator. |
What this calculator solves
Tape measures, lumber and floor plans in the United States use feet, inches and fractions of an inch. Adding 5 ft 7 1/2 in to 6 ft 8 3/4 in by hand means carrying fractions into inches and inches into feet. This calculator does that arithmetic exactly and shows the answer the way you would read it on a tape.
How the arithmetic works
Every length is first converted to inches: feet times 12, plus inches, plus the fraction. The operation is done on those totals, and the answer is split back into feet, whole inches and the nearest fraction. Working in inches avoids the carrying mistakes that happen when feet and inches are added separately.
5′ 7½″ = 67.5 in6′ 8¾″ = 80.75 in67.5 + 80.75 = 148.25 in = 12′ 4¼″Reading fractions on a tape measure
Most tape measures mark sixteenths of an inch. The half-inch mark is the longest between inch lines, followed by quarters, eighths and sixteenths. Fractions are always reduced, so 8/16 is shown as 1/2 and 12/16 as 3/4.
Multiplying and dividing lengths
Multiply to repeat a length, such as seven shelves of 2 ft 10 1/4 in. Divide to split a length evenly, such as a 10 ft wall into three equal panels. When dividing a board into pieces, remember that each cut removes the width of the saw blade, so the pieces come out slightly shorter than the math suggests.
Rounding and precision
The result is rounded to the nearest 1/16 inch by default, which is the finest mark on most tapes. Choose 1/8 or 1/4 inch for rough framing, or 1/32 inch for finer work. The detail rows show the rounding adjustment so you can see what was dropped.
Decimal feet and metric
Estimators and spreadsheets often need decimal feet: 12 ft 4 1/4 in is 12.354 feet. An inch is exactly 2.54 centimeters, so the metric equivalents shown here are exact before rounding.
Fractions of an inch as decimals
| Fraction | Decimal inch | Millimeters |
|---|---|---|
| 1/16 in | 0.0625 | 1.59 mm |
| 1/8 in | 0.125 | 3.17 mm |
| 3/16 in | 0.1875 | 4.76 mm |
| 1/4 in | 0.25 | 6.35 mm |
| 5/16 in | 0.3125 | 7.94 mm |
| 3/8 in | 0.375 | 9.52 mm |
| 7/16 in | 0.4375 | 11.11 mm |
| 1/2 in | 0.5 | 12.70 mm |
| 9/16 in | 0.5625 | 14.29 mm |
| 5/8 in | 0.625 | 15.88 mm |
| 11/16 in | 0.6875 | 17.46 mm |
| 3/4 in | 0.75 | 19.05 mm |
| 13/16 in | 0.8125 | 20.64 mm |
| 7/8 in | 0.875 | 22.22 mm |
| 15/16 in | 0.9375 | 23.81 mm |
Frequently asked questions
How do I add feet and inches?
Add the inches and fractions first, carry every 12 inches into one foot, then add the feet. The calculator does this by converting everything to inches.
How do I subtract feet and inches?
Convert both lengths to inches, subtract, and convert back. If the second length is larger, the result is shown as a negative length.
How do I convert feet and inches to decimal feet?
Divide the inches by 12 and add them to the feet: 4 1/4 in is 4.25 ÷ 12 = 0.354 ft.
How many inches are in a foot?
Twelve. A yard is 3 feet or 36 inches.
What does 5′ 7″ mean?
The single mark (′) means feet and the double mark (″) means inches, so 5′ 7″ is 5 feet 7 inches.
How do I convert inches to centimeters?
Multiply by 2.54. One inch is exactly 2.54 centimeters.
Why does my cut piece come out short?
The saw blade removes material (the kerf) with every cut. Add it to your measurements when cutting several pieces from one board.
What to keep in mind
Rounding to 1/16 inch can hide up to 1/32 inch per result. For cuts, also allow for the saw blade's kerf and measure twice.
Results are rounded for display in US format, with money in dollars and cents; CSV exports keep full calculation precision. This is a calculation summary, not an official certificate.