Feet and Inches Calculator
This free feet and inches calculator does tape-measure math without the carrying. Enter each reading as feet, inches and a fraction (5′ 7 3/8″), add or subtract as many as you need, and get the total as feet-inches, plain inches, decimal feet, decimal inches and metric, rounded to the nearest 1/16″ or whatever precision you pick.
Switch to divide mode to split a wall, a fence run or a stair into equal parts. You get each part plus a list of layout marks measured from one end, so rounding errors don't build up the way they do when you step off one part at a time. Convert mode turns a decimal from a plan, a laser measure or a spreadsheet (7.85 ft, 2,400 mm) into a tape reading.
Built on the inch, foot and yard as defined in NIST Handbook 44 and the exact 25.4 mm inch from NIST SP 811. The math runs on exact values and rounds once, at the end. No signup, no pricing. Have a decimal-only field in another calculator? Convert your reading here, then paste the decimal back in.
Measuring for material? Total your runs with the Linear Feet Calculator, get room area with the Square Footage Calculator, or lay out a stair with the Stairs Calculator.
Feet & Inches Calculator
Add and subtract tape-measure readings in feet, inches and fractions, divide a length into equal parts with layout marks, or convert decimal feet, decimal inches and metric into a reading you can find on a tape. Rounds to the nearest 1/16″ by default. Free, no signup.
What do you need to do?
Add up tape readings, split a length into equal parts, or turn a decimal or metric number into feet, inches and a fraction.
Measurements
Enter each reading as feet, inches and a fraction. Inches can go past 11 (30 in is fine) and can be decimal (7.375). Use − rows to subtract.
How to add feet and inches by hand
Add each column separately, then carry. Fractions first: put them over a common denominator (sixteenths are easiest), add, and carry every 16/16 into a whole inch. Then add the inches and carry every 12 inches into a foot. Then add the feet. For 5′ 7 3/8″ + 2′ 9 7/8″: 6/16 + 14/16 = 20/16, which is 1 inch and 4/16 (1/4″). The inches are 7 + 9 + 1 = 17, which is 1 foot and 5 inches. The feet are 5 + 2 + 1 = 8. The answer is 8′ 5 1/4″.
To subtract, borrow the other way: take a foot and turn it into 12 inches, or take an inch and turn it into 16/16, whenever the top number is smaller. The calculator skips the carrying entirely. It turns every reading into exact inches, does the math once, and rounds only the final answer to the tape fraction you pick. Rounding each reading before you add is how small errors build into a cut that misses by 1/4″.
Fraction to decimal chart (sixteenths)
Every 1/16″ step on a tape and its decimal-inch value. Fractions with 2, 4, 8 or 16 on the bottom convert to decimals exactly.
| Fraction | Decimal inch | Fraction | Decimal inch |
|---|---|---|---|
| 1/16″ | 0.0625 | 9/16″ | 0.5625 |
| 1/8″ | 0.125 | 5/8″ | 0.625 |
| 3/16″ | 0.1875 | 11/16″ | 0.6875 |
| 1/4″ | 0.25 | 3/4″ | 0.75 |
| 5/16″ | 0.3125 | 13/16″ | 0.8125 |
| 3/8″ | 0.375 | 7/8″ | 0.875 |
| 7/16″ | 0.4375 | 15/16″ | 0.9375 |
| 1/2″ | 0.5 | 1/1″ | 1 |
Calculation Formulas
Every reading is turned into one exact number of inches before any math, so feet, inches and fractions never get mixed up.
Example:
5′ 7 3/8″ = 5 × 12 + 7 + 0.375 = 67.375 in
Readings are summed as exact inches. Inches above 11 carry into feet automatically.
Example:
5′ 7 3/8″ + 2′ 9 7/8″ = 67.375 + 33.875 = 101.25 in = 8′ 5 1/4″
The exact total is rounded once, at the end, to the nearest division on the tape. Halves round up. The fraction is then reduced (8/16 → 1/2).
Example:
17.5714 in × 16 = 281.14 → 281 ÷ 16 = 17 9/16 in
Splits a rounded inch total into whole feet, whole inches and a fraction for a reading you can find on a tape.
Example:
101.25 in → 8 ft (96 in) + 5.25 in = 8′ 5 1/4″
Layout marks are measured from one end, each rounded once. Stepping off one rounded part at a time adds the rounding error at every mark.
Example:
10′ 3″ ÷ 7 = 17.571 in each = 1′ 5 9/16″; mark 3 = 52.714 in = 4′ 4 11/16″
Used for repeated pieces: stud heights, siding courses, cabinet boxes.
Example:
92 5/8″ × 14 = 1,296.75 in = 108′ 0 3/4″
Plans and laser measures often give decimal feet. Multiply by 12, then round to a tape fraction.
Example:
7.85 ft × 12 = 94.2 in = 7′ 10 3/16″
The inch is defined as exactly 25.4 mm, so this conversion has no rounding of its own.
Example:
1,000 mm ÷ 25.4 = 39.37 in = 3′ 3 3/8″
Standard Constants
| Constant | Value | Description |
|---|---|---|
| Inches per foot | 12 | U.S. customary length (NIST Handbook 44). |
| Feet per yard | 3 | U.S. customary length (NIST Handbook 44). |
| Millimeters per inch | 25.4 (exact) | Fixed by the 1959 international yard and pound agreement; listed as exact in NIST SP 811. |
| Standard tape division | 1/16 in | The finest mark on most carpentry tape measures. Some tapes add 1/32 in on the first foot. |
| Default rounding | Nearest 1/16 in | Rounded once at the end. Halves round up. |
| 1/16 in in decimal | 0.0625 in | Fractions with power-of-two denominators convert to decimals exactly. |
| Stud layout marks | 16 in o.c. | Highlighted on most tapes; IRC Table R602.3(5) allows 16 or 24 in stud spacing. |
| Truss / joist layout marks | 19.2 in | The small diamonds on many tapes: five spaces per 8 ft sheet. |
Note: All calculations include appropriate waste factors based on project complexity and material type. Results are estimates and should be verified by professionals before purchasing materials.
NIST Handbook 44 — Units of Length(NIST HB 44)
View StandardDefines the U.S. customary length units used on tape measures and in trade (inch, foot, yard), and includes the code for linear measures used in commerce.
Key Requirements:
- •1 foot = 12 inches
- •1 yard = 3 feet = 36 inches
- •Tolerances for rules and tapes used in commerce
NIST SP 811 — Guide for the Use of the SI(NIST SP 811 (2008))
View StandardNIST's conversion guide. Its conversion-factor appendix lists inch to meter as an exact factor.
Key Requirements:
- •1 inch = 0.0254 m (exact)
- •1 foot = 0.3048 m (exact)
U.S. Survey Foot Deprecation(NIST / NOAA (Federal Register, 2020))
View StandardThe U.S. survey foot (1200/3937 m) was deprecated at the end of 2022. The international foot (0.3048 m) is the one foot for new work.
Key Requirements:
- •International foot = 0.3048 m exactly
- •Survey foot differs by about 2 parts per million (about 1/8 in per mile)
IRC Table R602.3(5) — Stud Spacing(IRC R602.3)
View StandardSets wood stud size, height and spacing for wall framing, the source of the 16 in and 24 in on-center layouts marked on tapes.
Key Requirements:
- •Common stud spacing: 16 in or 24 in on center
- •Layout is measured from one end, not stepped off
DOC PS 20 — American Softwood Lumber Standard(DOC PS 20)
View StandardDefines nominal vs actual (dressed) lumber sizes, the reason a 2×4 measures 1 1/2 × 3 1/2 in on the tape.
Key Requirements:
- •Nominal 2× = 1 1/2 in actual thickness
- •Nominal 4 = 3 1/2 in, nominal 6 = 5 1/2 in actual width
Standards Disclaimer: Standards and codes are subject to periodic updates. Always verify current requirements with local building authorities and professional engineers before beginning construction. Links provided are for reference only.
Architectural vs. Civil Drawings
Feet-inches vs. decimal feet
Architectural plans dimension in feet, inches and fractions (12′-6 1/2″). Site plans, surveys and grading plans usually use decimal feet to the hundredth (12.54′).
Regional Examples:
Survey Foot vs. International Foot
Older land records
Pre-2023 surveys and state plane coordinates in some states used the U.S. survey foot. The difference is about 2 parts per million: invisible on a building, but it shows up over miles.
Regional Examples:
Canada and Metric Plans
Imperial trades, metric documents
Canadian building trades still buy lumber and sheet goods in imperial sizes, but many plans and product specs are metric. Imported cabinets and fixtures are often specified in millimeters.
Regional Examples:
Precision by Trade
How fine to round
Rough framing is cut to 1/16 in at best and often to 1/8 in. Finish carpentry, cabinetry and countertop templates work to 1/32 in. Concrete forms and sitework are usually fine at 1/4 in.
Regional Examples:
Tape Measure Markings
What the extra marks mean
Most U.S. tapes highlight 16 in multiples for stud layout and add small diamonds every 19.2 in for joist and truss layout (five spaces per 8 ft sheet). Some tapes mark the first foot in 1/32 in.
Regional Examples:
Before You Build
- •Contact your local building department for specific requirements
- •Verify frost line depths, wind zones, and seismic requirements for your area
- •Check if permits are required and schedule required inspections
- •Consult with a local contractor familiar with local codes
Have your feet-and-inches measurement? Drop it into a project calculator
These calculators take this number as an input — pick your project and carry the figure straight over.
Cabinets & Countertops
Decks & Fences
Doors, Windows & Trim
Framing & Structure
Measuring & Estimating
Paint & Wallpaper
Related Calculators
Linear Feet Calculator
Free linear feet calculator: get running feet from a perimeter, a list of runs, or square feet. Subtract openings, see sticks to buy. No signup.
Stairs Calculator
Code-compliant stair geometry, stringers & materials per 2021 IRC R311.7 / 2024 R318.7. Straight, L, U, winder, spiral & curved. AWC DCA 6 stringer spans. Free.
Square Footage Calculator
Free square footage calculator: add multiple rooms or odd shapes, subtract doors and windows, and convert to sq ft, sq yards, square meters and squares.
How to Use This Calculator
- Pick a mode: Add & subtract measurements, Multiply or divide a measurement, or Convert decimal or metric to feet-inches.
- Pick how finely to round the answer. 1/16″ matches a standard tape; use 1/32″ for finish work or 1/8″ for rough framing.
- Add mode: enter each reading as feet, inches and a fraction. Inches can go past 11 and can be decimal. Set the second and later rows to + or −.
- Divide mode: enter the length and the number of equal parts to get each part and the layout marks from one end. Multiply mode: enter the length and how many times to repeat it.
- Convert mode: enter a decimal value and pick its unit (decimal feet, decimal inches, yards, mm, cm or m).
- Click Calculate to see the answer as feet-inches, inches with a fraction, decimal feet, decimal inches, yards and metric, plus the rounding note.
- Copy the decimal into any calculator that takes decimal feet or inches, such as the Stairs, Trim or Window calculators.
Why Round Once, at the End
A tape measure reads to 1/16″, so every reading is already rounded by up to 1/32″. If you also round each step of the math, the errors add up: ten pieces each rounded 1/32″ long make a run that is 5/16″ long. This calculator keeps every reading as an exact number of inches, adds, subtracts, multiplies or divides those exact values, and rounds only the final answer to the tape fraction you choose. It also tells you how far the rounded reading is from the exact value. The same rule is why divide mode lists layout marks measured from one end: each mark is rounded once from the exact position, instead of carrying the rounding of every previous part.
Frequently Asked Questions
How do you add feet and inches with fractions?
Add each part separately and carry. Fractions first: convert to sixteenths, add, and carry every 16/16 into a whole inch. Then add the inches and carry every 12 into a foot. Then add the feet. Example: 5′ 7 3/8″ + 2′ 9 7/8″. The fractions are 6/16 + 14/16 = 20/16, which is 1″ and 1/4″. The inches are 7 + 9 + 1 = 17, which is 1′ 5″. The feet are 5 + 2 + 1 = 8. Total: 8′ 5 1/4″. The calculator does this for any number of readings.
How do I convert decimal feet to feet and inches?
Keep the whole feet, multiply the decimal part by 12 to get inches, then turn the leftover decimal inch into sixteenths. For 7.85 ft: 0.85 × 12 = 10.2 in, and 0.2 × 16 = 3.2, which rounds to 3/16. So 7.85 ft is 7′ 10 3/16″. Site plans and surveys use decimal feet; floor plans and tape measures use feet and inches, so this conversion comes up whenever you lay out from a civil drawing.
How do I divide a length into equal parts?
Convert the length to inches, divide by the number of parts, then measure every mark from the same end. For a 10′ 3″ wall split into 7 bays: 123 ÷ 7 = 17.571 in, about 1′ 5 9/16″ each. Mark 1 is 17 9/16″, mark 2 is 35 1/8″, mark 3 is 52 11/16″, and so on, each measured from the start. Stepping off 17 9/16″ seven times instead would land the last mark about 1/16″ short. Divide mode lists every mark for you.
How do I convert millimeters or meters to feet and inches?
Divide millimeters by 25.4 to get inches; the inch is defined as exactly 25.4 mm, so there's no rounding in the conversion itself. Then split the inches into feet and inches and round the fraction. 600 mm is 23.62 in, about 23 5/8″, the standard width of a European base cabinet. 1 meter is 39.37 in, about 3′ 3 3/8″. Pick millimeters, centimeters or meters in Convert mode.
What fraction of an inch should I round to?
Round to what you can find and cut. A standard tape is marked in 1/16″, so 1/16″ is the default. Rough framing is fine at 1/8″. Finish trim, cabinets and stair parts are often cut to 1/32″, and some tapes mark 1/32″ on the first foot. Forms, fence layout and grading rarely need better than 1/4″. The calculator does all the math on exact values and rounds only the final answer, then shows how far the rounded reading is from the exact length.
Why do my added-up measurements come out slightly off?
Usually because each reading was rounded before it was added. Every tape reading can be off by up to half a mark (1/32″ on a 1/16″ tape), and those small errors add up across many pieces: ten pieces each read 1/32″ long make a run 5/16″ long. Add the readings exactly and round once at the end, which is what this calculator does. Also check that you didn't mix up readings taken from the hook end and the case end of the tape, which differ by the case length.
How many inches is a 2×4 or a 2×6?
Lumber is named by its nominal size, not its actual size. Under the American Softwood Lumber Standard (DOC PS 20), a dry 2×4 is 1 1/2″ × 3 1/2″, a 2×6 is 1 1/2″ × 5 1/2″, a 2×8 is 1 1/2″ × 7 1/4″ and a 2×10 is 1 1/2″ × 9 1/4″. When you add up a stack of lumber, such as three 2× plates on a wall, use the actual thickness: 3 × 1 1/2″ = 4 1/2″, not 6″.