Add, convert and split measurements in feet and inches
Add or subtract lengths, convert decimals to fractions, and get area — to the nearest 1/16". Free, no email required to see the math.
Your inputs
Add, subtract, multiply or divide lengths. Left to right. Fractions to 1/16".
You'll need
The math, in plain English.
Type measurements the way you'd read them off a tape — 10' 6", 10-6, 126.5", 6 1/2", even 10' 6-1/2" — and add, subtract, multiply or divide them. It works like a tape calculator: left to right, no order of operations, so 10' + 2' × 3 is 36 feet, not 16. Multiply and divide take a plain number on the right (÷ 3 to split a wall into three equal bays). Everything is converted to inches under the hood and the answer comes back rounded to the nearest 1/16", which is as fine as a tape reads.
Convert mode takes one value in any form and shows it every other way — decimal feet for a plan, decimal inches for a saw with a digital readout, and the feet-inches-fraction you'd actually mark on the board. Area mode is the quick one for flooring, paint, and drywall takeoffs: length × width in square feet and square inches.
Use this to convert measurements for our other calculators. Every length field on this site accepts the same formats, but when you need to add up three wall segments before you drop them into the paint calculator, or divide a stair rise into equal parts, this is the scratchpad. Remember that lumber and trim sizes are nominal — a 2×4 is 1-1/2" × 3-1/2" — so measure the actual stock, not the name on the tag.
Feet-Inches questions
Why is a 2×4 not actually 2 inches by 4 inches?+
The "2×4" is the rough-sawn size before the mill dries and planes the board smooth. What you buy is 1-1/2" × 3-1/2". The same shrink applies across dimensional lumber: a 2×6 is 1-1/2" × 5-1/2", a 4×4 is 3-1/2" square, and a 1× board is 3/4" thick. Always lay out with the actual size.
How do I add feet and inches by hand?+
Add the inches first, then the feet, then carry: every 12 inches becomes a foot. For fractions, put everything over 16 — 1/2" is 8/16, 3/8" is 6/16 — add the numerators, and carry every 16 into a whole inch. Or type it here and skip the arithmetic.
How do I read a tape measure to 1/16 of an inch?+
Between each inch mark there are 15 smaller lines. The longest is 1/2", the next two longest are 1/4" and 3/4", the mid-length ones are eighths, and the shortest are sixteenths. Count sixteenths from the last whole inch, then simplify: 8/16 is 1/2, 12/16 is 3/4. The little black diamonds every 19-3/16" are truss layout marks — ignore them for normal work.
What does 16 inches on-center mean?+
The distance from the center of one stud, joist, or rafter to the center of the next is 16 inches, so a 4-foot sheet of drywall or plywood lands on a framing member at both edges and in the middle. The red numbers on a tape are the on-center marks. 24" on-center is the other common spacing for roof trusses and some floor systems.
Why does the answer show a fraction instead of a decimal?+
Because that is what you can find on a tape. 10.54 feet is 10' 6-1/2" — the decimal is fine on a plan or in a spreadsheet, but the fraction is what gets marked on the board. Both are shown so you can use whichever the tool in your hand reads.
Does this work on my phone without a signal?+
Yes. The math runs in your browser, so once the page has loaded it keeps working in a crawlspace, a basement, or a jobsite with no coverage. Add it to your home screen and it opens like an app.
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