Add two lengths
Show the working
5′ 3 1/2″ is 63.5 in and 2′ 8 3/4″ is 32.75 in. Together that is 96.25 in, which is 8 feet with 0.25 in over, written 8′ 0 1/4″. In millimetres it is 2444.8 mm.
Feet and Inches Calculator: Add, Subtract, Convert
Calculator
Result
5′ 3 1/2″ + 2′ 8 3/4″ = 8′ 0 1/4″. That is 96.25 in, 8.0208 ft or 2444.8 mm.
Answer
8′ 0 1/4″
96.25 in, to the nearest 1/16 in.
Decimal inches
96.25 in
96.25 in once rounded to 1/16 in.
Decimal feet
8.0208 ft
Millimetres
2444.8 mm
244.47 cm · 2.445 m
Working in inches: 96.25 = 96.25 = 96.25.
This length falls exactly on a 1/16 in mark, so nothing was rounded.
Adding feet and inches by hand means carrying twelves, borrowing a foot and reducing sixteenths, and one slip puts a cut a quarter inch off. This feet and inches calculator does the carrying as you type. It adds, subtracts, multiplies and divides lengths, then shows the answer as a tape reads it, plus decimals and millimetres. It reads like a tape measure calculator, and it allows the construction-site habit of mixing feet and metric.
- Free
- No signup
- Reviewed 15 October 2026
- Estimates only
Quick answer 5′ 3 1/2″ plus 2′ 8 3/4″ is 8′ 0 1/4″ (96.25 in, 8.0208 ft, 2444.8 mm). Add up to four lengths, take one off, then multiply or divide, in feet, inches, fractions or metric.
How it works
Every length is turned into inches first: feet times 12, plus the inches, plus the fraction. That one rule is the whole inch calculator. Divide by 12 and you have feet, multiply by 12 and you have inches, which is how a feet inches calculator converts both ways. Metric joins in at exactly 25.4 mm to the inch, so a 2400 mm sheet and an 8′ stud can share one sum.
The lengths are added, the Subtract length comes off, and only then are the total multiplied and divided. Nothing is rounded on the way. That matters on a cut list: ten pieces each rounded to the nearest 1/16 can be out by up to 5/16 in by the end of the run.
The answer is rounded once, to the nearest 1/2, 1/4, 1/8, 1/16, 1/32 or 1/64 in, and written as feet, whole inches and a reduced fraction, the way a carpenter fraction calculator should. The decimal inches, decimal feet and millimetres come from the exact value, and the result says how far the rounding moved it. A tape reads to 1/16, so that is the default.
Got the length? Put it to work. The rafter length calculator turns a run into a rafter, the stair calculator splits a rise into equal risers, and the baluster calculator spaces a guard evenly.
Formula
L1 to L4 = lengths to add, S = length to subtract, m = multiplier, d = divisor, n = fractions of an inch (16 for sixteenths), R = the exact result in inches.
total = L1 + L2 + L3 + L4 − S result = total × m ÷ d feet = result ÷ 12 mm = result × 25.4 shown = round(result × n) ÷ n n = 2, 4, 8, 16, 32 or 64
Worked examples
Cut a board, split the rest in four
Show the working
A 16 ft board is 192 in. Take off a 3′ 9 5/8″ cut (45.625 in) and 146.375 in is left. Divided into 4 equal pieces that is 36.59375 in each. A tape reads to 1/16, so each piece is 3′ 0 5/8″, which is 0.0313 in over the exact value.
13 risers at 7 3/8 in
Show the working
Each riser is 7 3/8 in, which is 7.375. Thirteen of them make 95.875 in, or 7′ 11 7/8″. That is the total rise the stairs have to cover.
A metric board plus an imperial one
Show the working
2.4 m is 94.488 in and 1250 mm is 49.213 in. The sum is 3650 mm, or 143.701 in. To the nearest 1/16 in that is 11′ 11 11/16″.
Inch fractions and feet and inches to decimal
Keep these two within reach. The first turns every tape-measure fraction into a decimal inch and millimetres. The second turns whole inches into a decimal fraction of a foot. They run on the same code as the calculator above, so they cannot disagree with it.
| Fraction | Decimal in | mm |
|---|---|---|
| 1/16″ | 0.0625 | 1.6 |
| 1/8″ | 0.1250 | 3.2 |
| 3/16″ | 0.1875 | 4.8 |
| 1/4″ | 0.2500 | 6.3 |
| 5/16″ | 0.3125 | 7.9 |
| 3/8″ | 0.3750 | 9.5 |
| 7/16″ | 0.4375 | 11.1 |
| 1/2″ | 0.5000 | 12.7 |
| 9/16″ | 0.5625 | 14.3 |
| 5/8″ | 0.6250 | 15.9 |
| 11/16″ | 0.6875 | 17.5 |
| 3/4″ | 0.7500 | 19.0 |
| 13/16″ | 0.8125 | 20.6 |
| 7/8″ | 0.8750 | 22.2 |
| 15/16″ | 0.9375 | 23.8 |
| 1″ | 1.0000 | 25.4 |
| Inches | Decimal ft | mm |
|---|---|---|
| 1″ | 0.0833 | 25.4 |
| 2″ | 0.1667 | 50.8 |
| 3″ | 0.2500 | 76.2 |
| 4″ | 0.3333 | 101.6 |
| 5″ | 0.4167 | 127.0 |
| 6″ | 0.5000 | 152.4 |
| 7″ | 0.5833 | 177.8 |
| 8″ | 0.6667 | 203.2 |
| 9″ | 0.7500 | 228.6 |
| 10″ | 0.8333 | 254.0 |
| 11″ | 0.9167 | 279.4 |
How to read a measuring tape
Every inch on a tape is cut into equal steps, and the shorter the line, the smaller the fraction. Take the last whole-inch number you passed, count the small marks past it, and call the count sixteenths. Ten marks past the 3 is 3 10/16″, which reduces to 3 5/8″ (3.625 in). The length of the line gives away the reduced fraction: the half-inch line sits 8 marks past an inch number, and the quarter-inch lines sit 4 and 12 past. Type what you read into the calculator above and it works as a tape measure calculator: it adds, subtracts and converts the reading for you.
| Line | Marks that length | Marks per inch, this size and longer | Decimal inch |
|---|---|---|---|
| Inch line, the longest | 1″ | 1 | 1.0000 |
| Half inch | 1/2″ | 2 | 0.5000 |
| Quarter inch | 1/4″, 3/4″ | 4 | 0.2500 |
| Eighth inch | 1/8″, 3/8″, 5/8″, 7/8″ | 8 | 0.1250 |
| Sixteenth inch, the shortest | 1/16″, 3/16″, 5/16″, 7/16″, 9/16″, 11/16″, 13/16″, 15/16″ | 16 | 0.0625 |
Decimal to fraction chart for inches
A spec sheet says 0.3 and your tape only knows fractions. This works as a decimal to fraction calculator for inches: type the decimal into Length 1 as a plain number, pick 1/16, 1/32 or 1/64, and read the nearest mark. The table is the same rounding done for common decimals. It is for inches only, so a decimal that is not a length belongs in a general fraction tool.
| Decimal inches | Nearest 1/16 | Nearest 1/32 | Nearest 1/64 |
|---|---|---|---|
| 0.1 | 1/8″ | 3/32″ | 3/32″ |
| 0.125 | 1/8″ | 1/8″ | 1/8″ |
| 0.2 | 3/16″ | 3/16″ | 13/64″ |
| 0.25 | 1/4″ | 1/4″ | 1/4″ |
| 0.3 | 5/16″ | 5/16″ | 19/64″ |
| 0.4 | 3/8″ | 13/32″ | 13/32″ |
| 0.5 | 1/2″ | 1/2″ | 1/2″ |
| 0.6 | 5/8″ | 19/32″ | 19/32″ |
| 0.7 | 11/16″ | 11/16″ | 45/64″ |
| 0.75 | 3/4″ | 3/4″ | 3/4″ |
| 0.8 | 13/16″ | 13/16″ | 51/64″ |
| 0.9 | 7/8″ | 29/32″ | 29/32″ |
Inches to feet and feet to inches conversion
Type a length into the calculator above and it is an inches to feet calculator. Type feet and it is a ft to inches calculator. Either way you get feet and inches, decimal feet, decimal inches, centimetres and millimetres. The tables below are the same conversions for lengths you meet all the time: divide inches by 12 to get feet, multiply feet by 12 to get inches.
| Inches | Feet and inches | Decimal feet |
|---|---|---|
| 6 in | 6″ | 0.5 |
| 12 in | 1′ | 1 |
| 18 in | 1′ 6″ | 1.5 |
| 24 in | 2′ | 2 |
| 30 in | 2′ 6″ | 2.5 |
| 36 in | 3′ | 3 |
| 48 in | 4′ | 4 |
| 60 in | 5′ | 5 |
| 72 in | 6′ | 6 |
| 96 in | 8′ | 8 |
| 100 in | 8′ 4″ | 8.3333 |
| 120 in | 10′ | 10 |
| Feet | Inches | mm |
|---|---|---|
| 1 ft | 12 | 304.8 |
| 2 ft | 24 | 609.6 |
| 3 ft | 36 | 914.4 |
| 4 ft | 48 | 1219.2 |
| 5 ft | 60 | 1524 |
| 6 ft | 72 | 1828.8 |
| 8 ft | 96 | 2438.4 |
| 10 ft | 120 | 3048 |
| 12 ft | 144 | 3657.6 |
| 16 ft | 192 | 4876.8 |
| 20 ft | 240 | 6096 |
| 24 ft | 288 | 7315.2 |
| Feet and inches | Decimal feet | Decimal inches | cm |
|---|---|---|---|
| 5′ 3 1/2″ | 5.2917 | 63.5 | 161.3 |
| 6′ 8″ | 6.6667 | 80 | 203.2 |
| 8′ 1 1/2″ | 8.125 | 97.5 | 247.7 |
| 10′ 4 1/4″ | 10.3542 | 124.25 | 315.6 |
| 12′ 8″ | 12.6667 | 152 | 386.1 |
Code notes
This tool does not check a building code. It is arithmetic on lengths, so no code section applies. The stair, rafter and baluster calculators do the code checks.
One inch is exactly 25.4 mm, fixed by the 1959 international yard and pound agreement, so converting feet and inches to millimetres is exact before any rounding.
Drawings often write 5′-3 1/2″ with a dash between the feet and the inches. The calculator reads that as 5 feet 3 1/2 inches, and so is 6-3 1/2. A bare number counts as inches, or as millimetres when the units are metric.
Section numbers refer to IRC 2021 section numbers; England Approved Document K. Local amendments are common, so confirm with your building authority.
FAQ
Hover a question to read the answer. Click to keep it open.Tap a question to open it.
How do you add and subtract feet and inches?
To add, add feet to feet and inches to inches, then carry: every 12 inches becomes a foot. 5′ 3 1/2″ plus 2′ 8 3/4″ is 7 feet and 12 1/4 inches, which carries to 8′ 0 1/4″. To subtract, borrow a foot when the top inches are smaller: 10′ 2″ minus 3′ 9″ is 9′ 14″ minus 3′ 9″, which is 6′ 5″. In the calculator, put the longer length in Length 1 and the shorter one in Subtract, and the carrying and borrowing is done for you, for up to four lengths.
How do you multiply or divide feet and inches?
Convert to inches, multiply or divide, then convert back. 13 risers of 7 3/8 in is 13 × 7.375 = 95.875 in, which is 7′ 11 7/8″. Use Multiply by for a count and Divide by to split a length into equal parts.
How do you convert inches to feet?
Divide the inches by 12. 100 in is 8.3333 ft, which is 8 feet 4 inches. To go the other way, multiply the feet by 12: 8 ft is 96 in. Type either one into Length 1 and the result shows feet and inches, decimal feet, decimal inches and millimetres.
How do you convert feet and inches to decimal?
Divide the inches by 12 and add the feet. 5′ 3 1/2″ is 5 + 3.5 ÷ 12 = 5.2917 ft, or 63.5 in. That is the feet and inches to feet conversion that spreadsheets and CAD files want, and the result shows it next to the feet-and-inches answer.
How do you turn a decimal into a fraction of an inch?
Type the decimal into Length 1 as a plain number, which counts as inches, and pick the fraction size. 6.4375 in is 6 7/16″ at 1/16. A decimal that does not land on a mark is rounded to the nearest one: 0.3 in becomes 5/16″, which is 0.0125 in more.
How do you read a measuring tape?
Find the last whole-inch number before your point, then count the small marks past it. The marks get shorter as the fraction gets smaller: half inch, quarter inch, eighth, sixteenth. A point 10 marks past the 3 on a tape marked in sixteenths is 3 10/16″, which reduces to 3 5/8″. Type the reading into the calculator to add it to other measurements or convert it to millimetres.
How do you convert feet and inches to cm?
Turn the length into inches and multiply by 2.54. A length of 63.5 in (5′ 3 1/2″) is 161.29 cm, or 1612.9 mm. Type it into Length 1 and the centimetres and millimetres show under the answer.
Can I mix metric and imperial, and how many millimetres are in an inch?
Yes. Each length takes its own units: 2400mm, 1.2m, 8', 5 ft 3 in or 5' 3 1/2". One inch is exactly 25.4 mm, so a foot is 304.8 mm and a 2400 mm sheet is 94.49 in, which is 94 1/2″ to the nearest 1/16. The answer shows feet and inches, decimals and millimetres, whichever you typed.