Fabric math, done for you
Whether you're piecing a quilt back, cutting binding strips, or buying fabric for a whole wall of drapes, the hardest part often is not the sewing; it is the math. You have to convert between inches, yards, centimeters, and meters, account for the usable width of your fabric, add the right hem, seam, and fullness allowances, and then round up so you don't get to the cutting counter and come up short. Fabric Math is a free collection of online fabric calculators that does all of that for you, instantly, with no spreadsheets, no sign-up, and no clutter around the answer.
Every tool is built mobile-first, so you can pull it up on your phone right at the cutting table or in the aisle of the fabric store. Type in your measurements and the result appears immediately, and because each calculator shows the exact formula it used, you can always check the math yourself instead of trusting a black box.
A calculator for every fabric project
Fabric Math currently includes four free calculators, each built around one common "how much fabric do I need?" question:
- Quilt backing calculator: works out backing yardage, how many panels to piece, and which way the seams should run, for everything from a baby quilt to a king.
- Quilt binding calculator: tells you how many cross-grain strips to cut and how much binding fabric to buy, including extra for corners and diagonal joins.
- Curtain & drapery calculator: calculates curtain yardage using the correct fullness ratio, pattern repeat, hems, and returns for grommet, rod-pocket, and pinch-pleat headings.
- Fabric yardage calculator: the general-purpose tool for cutting any number of same-size pieces, with a waste allowance and inches-to-yards conversion built in.
Imperial or metric, your choice
Sewing is a global craft, so every calculator switches instantly between imperial (inches and yards) and metric (centimeters and meters) with a single tap. Your preference is remembered on your device, and the default fabric widths update automatically, with 42 inches or 107 cm for quilting cotton, and 54 inches or 137 cm for home-décor and drapery fabric.
What is width of fabric (WOF)?
Almost all fabric math depends on the usable width of fabric, or WOF, which is the width left after you trim the selvages and straighten the grain. Quilting cotton is usually 40–42 inches, dressmaking and home-décor fabric is often 54–60 inches, and extra-wide quilt backing reaches 108 inches. The wider the fabric, the more pieces fit across each row and the less total length you need to buy, which is why every Fabric Math calculator lets you set the WOF to match the bolt you're actually buying.
Always buy a little extra
Even a perfect calculation is only an estimate, because real fabric shrinks in the wash, frays at the edges, and rarely cuts perfectly on grain. Every Fabric Math tool deliberately rounds up to the nearest ⅛ yard or 0.1 meter, so the number you see leans toward buying slightly more rather than risking a project-stopping shortage. For directional prints, large pattern repeats, or your very first run at a new pattern, it's wise to add a little more on top. Fabric is far cheaper than the heartbreak of running out two seams from the finish line.
Free to use, always
Fabric Math is completely free, with no account, no paywall, and no email required. Your measurements never leave your browser. Nothing is uploaded or stored on a server, and you can share any result as a link that carries your exact inputs, so it's easy to send a fabric shopping list to yourself or your local quilt shop.