How this instrument works
Binding is the folded strip of fabric sewn around a quilt's raw outer edge to enclose the top, batting, and backing in one finished border. The strip has to run the full way around the quilt — its perimeter — plus a bit more, because mitering each of the four corners and joining the strip ends together both consume extra length beyond the bare perimeter measurement.
Quilters conventionally add about 10 inches of allowance on top of the perimeter to cover this — enough slack to fold a clean miter at each corner and splice the strip's two ends together with a diagonal seam rather than a bulky straight one. This calculator adds that allowance directly to the perimeter you enter, so the result is the actual cut length of binding strip to piece together, not just the quilt's outer measurement.
This figure is a length, not a fabric area — it tells you how many inches of strip to end up with, not how many inches of fabric yardage to buy. Turning strip length into yardage requires knowing the strip's cut width and how many strips fit across a bolt of fabric (typically cut from selvage to selvage and pieced end to end), a separate step that depends on how wide you're cutting your binding strips.
- Enter the quilt's outer edge measurement in Quilt perimeter, inches — twice the width plus twice the length for a rectangular quilt.
- Enter Binding strip width, inches — the width you plan to cut your binding strips, commonly 2 to 2.5 inches for a standard double-fold binding.
- Enter Corner / joining allowance, inches — about 10 inches is the standard quilting convention for mitering corners and joining the strip ends.
- Read Binding strip length needed, inches — the perimeter plus the allowance, the total cut length of strip to piece together.
- Divide this length by your fabric's usable width (about 40 inches after removing selvages) to work out how many strips to cut and how much yardage to buy.
Worked example — a queen quilt with a 280-inch perimeter
Enter 280 into Quilt perimeter, inches and 10 into Corner / joining allowance, inches — a queen quilt finishing at 60 in x 80 in has a perimeter of 2 x (60 + 80) = 280 inches, and 10 inches is the standard allowance quilters add for mitering corners and joining the strip ends.
Binding strip length needed, inches adds the two together: 280 + 10 = 290 inches of binding strip to cut and piece — the actual length you need in hand once mitering and joining are accounted for, not just the bare 280-inch perimeter measurement.
Questions
Why do I need more binding than my quilt's exact perimeter?
Because mitering the four corners folds extra fabric into each turn, and joining the strip's two ends together with a diagonal seam needs overlap beyond where the strip closes the loop. A binding strip cut to the bare perimeter measurement, with nothing extra, will come up short right as you reach the final corner or the point where the ends need to meet.
Why is 10 inches the standard corner and joining allowance?
It's a widely used quilting rule of thumb that leaves enough slack to miter all four corners cleanly and still have room to splice the strip's two ends together with a diagonal seam rather than a bulky straight join. Some quilters add slightly more, 10 to 12 inches, for extra working room, especially on a first attempt at binding a quilt.
How do I turn this length into yards of fabric to buy?
Divide the total binding length by your fabric's usable width — commonly about 40 inches once selvages are trimmed off — and round up to get the number of strips you need to cut across the fabric. Multiply that strip count by your chosen strip width to get the total fabric length required, then convert inches to yards by dividing by 36.
Does the binding strip width affect how much length I need?
Not the total length of the finished binding strip itself — length is driven by the quilt's perimeter and the corner allowance, independent of how wide each strip is cut. Strip width does affect how many strips fit across a bolt of fabric and therefore how much yardage you need to buy to reach that total length, which is why this calculator tracks it separately from the length figure.
Is this the same fabric calculation as the quilt top area calculator?
No — they answer different questions. The quilt fabric calculator finds the area of fabric needed to piece the quilt top itself, while this calculator finds the length of binding strip needed to finish the edge afterward. Use both together: the top calculator for piecing, this one once you know your finished quilt's perimeter for binding.