Free Feet and Inches calculator
Add, subtract, multiply, and divide feet-and-inches measurements with tape-measure 1/16-inch fractions — and read every answer in decimal feet, yards, and metric, updated live, as you type.
On this page15 sections
Add and subtract give a length in feet and inches; multiply gives an area in square feet; divide gives how many times B fits into A. Fractions snap to 1/16 in; conversions use 1 ft = 0.3048 m.
Fractions are rounded to the nearest 1/16 inch. How accurate is this?
Results are estimates. Consult a professional.
How the feet and inches calculator works
Inches do not run in tens. There are 12 inches in a foot, so feet-and-inches math carries at 12, not at 10 — and that is exactly where mental arithmetic goes wrong on a job site. This calculator reduces each measurement to a single number of inches, runs the operation, then converts the answer back to feet, inches and a tape-measure fraction. It handles all four operations and shows the decimal equivalents alongside.
What each result gives you
Adding and subtracting two measurements returns a length — feet, inches and a fraction. Multiplying two lengths returns an area in square feet, because length times length is area, not a longer length. Dividing one length by another returns a plain number: how many of the second fit into the first. The calculator labels each result so you never mistake square feet for feet.
How to add and subtract feet and inches
Add the feet to the feet and the inches to the inches, then fix the overflow. When the inches total reaches 12 or more, subtract 12 and carry 1 foot. Subtraction works the same way in reverse: when you run short on inches, borrow a foot and add 12 inches before you take the difference.
- Convert each measurement to total inches: feet × 12 + inches + the fraction.
- Add or subtract the two inch totals.
- Carry every 12 inches back into a foot (or borrow a foot when subtracting).
- Reduce the leftover fraction to its simplest sixteenth — 8/16 becomes 1/2.
This is the same method the concrete calculator and other measurement tools use under the hood — reduce to one unit, do the math, convert back. The calculator does the carrying for you, which is where hand math most often slips.
A worked example: adding two measurements
A framer is laying out a wall from two stud spacings: 5 ft 7 1/2 in and 2 ft 9 3/4 in. She needs the combined length in feet and inches, plus the metric equivalent for the plan set.
Step 1 — Add the inches, with the fractions
Inches first: 7 1/2 + 9 3/4 = 7.5 + 9.75 = 17.25 in. That is more than 12, so it will carry.
Step 2 — Carry 12 inches into a foot
17.25 in = 1 ft 5.25 in. The 5.25 in is 5 1/4 in once you turn 0.25 back into a quarter. Carry the 1 ft forward.
Step 3 — Add the feet
5 ft + 2 ft + the carried 1 ft = 8 ft. The answer is 8 ft 5 1/4 in.
Step 4 — Read off the decimal equivalents
8 ft 5 1/4 in is 101.25 in total, 8.4375 ft in decimal feet, 2.8125 yd, and in metric 2.572 m (257.2 cm).
Working with inch fractions to 1/16
Most online tools convert your answer to a decimal and stop. On a job site you need it back as a fraction, because that is what the tape measure shows. This calculator keeps fractions to the nearest 1/16 inch — the finest standard tape mark — and reduces them, so 8/16 reads as 1/2 and 4/16 reads as 1/4.
To convert a fraction to a decimal, divide the top number by the bottom: 3/8 = 3 ÷ 8 = 0.375 in. To go the other way, the calculator multiplies the decimal part by 16, rounds to the nearest whole number of sixteenths, then reduces. A 1/16-inch result is more precise than 1/8 inch and matches how finish carpenters and cabinetmakers mark a cut.
| Fraction | Decimal inch | Decimal foot |
|---|---|---|
| 1/16 in | 0.0625 | 0.00521 |
| 1/8 in | 0.125 | 0.01042 |
| 1/4 in | 0.25 | 0.02083 |
| 1/2 in | 0.5 | 0.04167 |
| 3/4 in | 0.75 | 0.0625 |
| 1 in | 1.0 | 0.08333 |
Decimal-foot column = decimal inches ÷ 12. Rounding to 1/16 inch keeps results on a readable tape-measure mark.
How to multiply and divide feet and inches
Multiply and divide change the unit, and that trips people up. Multiplying two lengths gives an area, so the answer is in square feet, not feet. Dividing two lengths cancels the units entirely and leaves a plain count — how many of the smaller piece fit into the larger run.
Multiplying — length times length is area
For a 5 ft × 3 ft panel: 5 × 3 = 15 sq ft (2,160 sq in, or 1.39 m²). The calculator converts each measurement to decimal feet, multiplies, and labels the result as square feet so it is never read as a length. For room and surface areas, the concrete calculator applies the same length × width step.
Dividing — how many fit
A 10 ft run divided by a 2 ft 6 in spacing: 120 in ÷ 30 in = 4. The result is dimensionless — four spacings fit exactly. Division is how you count studs, joists, balusters or tiles across a length once you know the on-center spacing.
Convert feet and inches to decimal, yards, and metric
Every measurement here also reads out in decimal feet, total inches, yards, metres and centimetres. Decimal feet is what spreadsheets and estimating software expect; metric is what most plan sets outside the United States use. The conversions are exact, using the 1959 international factors.
So 8 ft 5 1/4 in is 8.4375 decimal feet, 101.25 total inches, 2.8125 yards, 2.5718 metres and 257.175 centimetres — all describing the same length.
Feet and inches conversion chart
If you want a ballpark before you reach for the calculator, this chart converts common feet-and-inches lengths to decimal feet and metric. These are exact, not rounded.
| Feet & inches | Decimal feet | Total inches | Metres |
|---|---|---|---|
| 1 ft 0 in | 1.0 | 12 | 0.305 |
| 2 ft 6 in | 2.5 | 30 | 0.762 |
| 5 ft 7 1/2 in | 5.625 | 67.5 | 1.715 |
| 8 ft 5 1/4 in | 8.4375 | 101.25 | 2.572 |
| 10 ft 0 in | 10.0 | 120 | 3.048 |
| 16 ft 0 in | 16.0 | 192 | 4.877 |
Decimal feet = total inches ÷ 12; metres = decimal feet × 0.3048. Values rounded to three decimals for display only.
Feet and inches definitions
Where this calculator helps on the job
Reach for it any time a measurement turns on feet-and-inches arithmetic — which is most of the time in framing, trim and layout work, where the carry at 12 is easy to fumble in your head.
- Adding up a wall or run — total several stud spacings, cabinet runs or trim pieces into one length.
- Cutting to fit — subtract a fitting or reveal from an opening to get the exact cut length.
- Squaring up areas — multiply length by width to get square feet for flooring, drywall or paint.
- Spacing and counts — divide a run by on-center spacing to count studs, joists, balusters or tiles.
- Working across unit systems — convert a feet-and-inches plan to metres for an imported fixture or a metric drawing.
How accurate is this feet and inches calculator?
The arithmetic is exact. Each measurement is reduced to a single decimal-inch value, the operation runs at full precision, and the unit conversions use the exact 1959 international factors — 0.3048 metres per foot, 2.54 centimetres per inch. If your inputs are right, the math is right to the decimal.
The only rounding is deliberate: fractional inches are snapped to the nearest 1/16, the finest mark on a standard tape measure. That means a raw decimal like 0.78 inch is shown as 13/16 inch, so the answer reads off a real tape rather than as an unusable decimal. Decimal feet, yards and metric outputs are not rounded by the engine; any rounding you see in the reference tables above is for display only. For volume and area estimates that build on these lengths, pair this with the relevant material tool — the lengths it gives you are exact to start from.
Frequently asked questions about the free Feet and Inches calculator
About this feet and inches calculator
This calculator runs entirely in your browser — nothing you type is sent anywhere. Each measurement is reduced to total inches, the operation runs at full precision, and the answer is converted back to feet, inches, and a 1/16-inch fraction with all the carries handled for you.
It is one of our construction calculators; browse the full set on the calculators home page.