Quilt Binding Calculator: Strips, Cut Widths, and Yardage

Quilt Binding Calculator

The binding math

Three steps produce the shopping number. First, total length: perimeter plus overage. Perimeter is 2 x (width + length), and the overage — 10 to 12 inches is the convention — pays for turning four mitered corners and for the overlap where the two ends of the binding meet and join. Second, strip count: straight-grain binding is cut across the width of the fabric, selvage to selvage, and after trimming selvages and losing a little to each diagonal join, a strip yields about 40 usable inches. Divide total length by 40 and round up. Third, yardage: multiply strip count by cut width and divide by 36, then round up to a cut the shop will make. Cut width is a genuine choice, not a default. Strips cut 2.5 inches are the forgiving standard — easier to fold over the edge, slightly wider finished look. Strips cut 2.25 inches produce a tighter, fuller binding that many quilters prefer with low-loft batting, because there is less empty fold to flatten over time; some go down to 2 inches for a very tight edge, which demands accurate piecing. Whatever you choose, cut every strip for the quilt at the same width — mixed widths telegraph immediately along a straight edge.

Worked example: binding a 60 x 80 quilt

Run the numbers for a 60 x 80 throw. Perimeter: 2 x (60 + 80) = 280 inches. Add 12 for corners and the final join: 292 inches of binding. Strip count: 292 divided by 40 usable inches is 7.3, so 8 strips — seven strips is 280 inches, which leaves you short right at the last corner, the most annoying place in quilting to run out. Yardage at a 2.5-inch cut: 8 x 2.5 = 20 inches of fabric, so buy 5/8 yard (22.5 inches), which leaves a comfortable margin for straightening the cut edge. At 2.25 inches: 8 x 2.25 = 18 inches, which is exactly half a yard with zero allowance — if the shop's cut is slightly off-grain or you square up the yardage first, you lose a strip, so 5/8 yard is still the safer purchase. The same method scales anywhere. A 36 x 52 crib quilt: perimeter 176, plus 12 is 188 inches, 5 strips, 12.5 inches of fabric — 1/2 yard. A 108 x 108 king: perimeter 432, plus 12 is 444 inches, 12 strips, 30 inches — a full yard. Notice binding barely responds to quilt size in dollars: even the king needs one yard, about $10 to $15 of fabric.

Straight-grain vs. bias binding

Straight-grain binding — strips cut selvage to selvage across the width — is the default for any quilt with straight edges, and the yardage math above assumes it. Bias binding, cut at 45 degrees to the grain, is required the moment your quilt has curves: scalloped borders, rounded corners, hexagon edges. Cross-grain strips have almost no stretch, so forcing them around a curve produces puckers and cupped edges; bias strips stretch smoothly around scallops and lie flat. Bias also wears longer, because the threads cross the quilt's edge at an angle and no single thread rides the fold taking all the abrasion — worth considering for a heavily used bed quilt even with straight edges. The yardage is computed differently and comes from a square. Multiply the binding length you need by the cut width, then take the square root: that is the side of the square of fabric that yields your continuous bias strip. For the 60 x 80 example, 292 inches x 2.5 inches = 730 square inches, and the square root is just over 27 — cut a 28-inch square, which means buying 7/8 yard. Expect bias to cost more fabric and more pressing time than the 5/8 yard straight-grain equivalent; that is the price of curves.

Double-fold French binding, the US standard

When patterns say binding without qualification, they mean double-fold French binding. The strip is pressed in half lengthwise, wrong sides together, and the two raw edges are aligned with the raw edge of the quilt sandwich and sewn through all layers with a quarter-inch-ish seam. The folded edge then wraps over the quilt's edge to the back and is stitched down by hand with a blind stitch or by machine. The payoff is durability: the quilt's edge — the part that gets grabbed, tucked, and washed hardest — ends up wearing two full layers of fabric, which is why double-fold outlasts single-fold binding by years on a working quilt. It also self-fills: a 2.25-inch strip folds to 1 1/8 inches, takes a 1/4-inch seam, and finishes in the neighborhood of 3/8 inch on each face, packed firm around the edge. A 2.5-inch strip finishes slightly wider with a bit more ease, which is friendlier when your quilt sandwich is thick with high-loft batting. Single-fold binding — one layer, raw edge turned under — still has a place on miniature quilts and wall hangings, where bulk matters more than wear. For anything that will be slept under or dragged to the couch, double-fold is the answer.

Scrappy binding

Scrappy binding — piecing the binding from leftover strips of many fabrics — is the traditional way to finish a scrap quilt, and the math changes less than you might expect. You still need the same total length, 292 inches for the 60 x 80 example, but you will make more joins, and every diagonal join consumes a couple of inches of strip, so add roughly 3 extra inches per additional segment beyond what a width-of-fabric calculation assumes. Keep individual segments at least 8 to 10 inches long; shorter pieces put lumpy diagonal seams so close together that the binding gets hard to fold evenly and the corners become a lottery — you do not want a join landing exactly on a miter. Two rules keep scrappy binding from looking accidental. Cut every segment to the identical width, 2.25 or 2.5 inches but never mixed, because width variation shows instantly along a straight edge. And plan the values, not just the prints: a scrappy binding that alternates light and dark reads as a deliberate piano-key frame, while random values can blur into the border. Fabric cost is effectively zero if you are cutting from scraps — which, on a quilt whose binding would otherwise cost 5/8 yard, is a small but satisfying win.