🧵 Quilt Fabric Calculator

How Much Fabric Does a Quilt Need?

Enter the finished quilt dimensions and block size, and the calculator returns the block count, backing yardage (assuming 44-inch fabric), and binding yardage with strip count. A 60x80 quilt with 12-inch blocks: 35 blocks (5 across, 7 down), 4.89 yards of backing, 0.49 yards of binding from 7 strips. Round up at the store and add 10 percent for safety.

The Method

Blocks round up because partial blocks still need whole fabric. Backing gets 8 extra inches (4 per side) for longarm quilting; if the quilt plus 8 exceeds 42 inches of usable fabric width, two lengths are seamed, doubling the yardage. Binding assumes 2.5-inch strips with 40 usable inches per strip after seams.

Worked Example

Sixty by 80 inches, 12-inch blocks: 60/12 = 5 across, 80/12 = 6.67, rounded up to 7 down: 35 blocks. Backing: (80+8)/36 = 2.44 yards per length; 60+8 = 68 inches wide needs 2 panels: 4.89 yards. Binding: perimeter 280 inches / 40 = 7 strips; 7 x 2.5 / 36 = 0.49 yards. Buy 5.5 yards of backing and half a yard of binding.

Standard Quilt Sizes

Common finished sizes: throw 50x60, twin 70x90, double 80x96, queen 90x108, king 108x108. Add 4-8 inches per side if the quilt must drape over a thick mattress. The calculator takes any dimensions, so measure the bed first and enter the real numbers.

Batting Too

Batting follows the backing logic: buy it 8 inches larger than the top in both directions, in one piece when possible. Packaged batting lists quilt sizes on the bag; compare against your dimensions rather than the name, since manufacturers size generously.

Fabric Shopping Tips

Buy backing and binding after the top is pieced, when measurements are real, not planned. Prewash if the top fabrics were prewashed, to keep shrinkage consistent. And the 10 percent rule: the most expensive fabric is the one you run out of mid-project and cannot match.

Quilt Math Shortcuts

Memorize three: backing is roughly length-plus-8-inches in yards, doubled for wide quilts; binding is about half a yard for anything under a queen; and blocks are just the grid multiplication. For scrappy tops, the block count is what matters most: it tells you how many 12-inch (or 10, or 8) squares to cut before you start chain-piecing. Count blocks first, buy fabric second.

Charity Quilt Sizes

Donation quilts have their own common targets: preemie quilts around 24x24, lap quilts 36x48, and single-bed charity quilts near 45x60. Guilds often specify exact sizes, so check before cutting. The calculator takes any dimensions, so enter the guild's spec and get the block count and yardage for exactly that target. Small quilts are also the fastest way to practice the math.

Keep a running notebook of every quilt's numbers: finished size, block count, backing bought, binding used. After three quilts you will estimate yardage from the finished size alone, and the calculator becomes the double-check rather than the starting point.

A Second Worked Example: The Queen Quilt

A 90 by 108 inch queen with 10-inch blocks. Blocks: 90 divided by 10 is 9 across; 108 divided by 10 is 10.8, round up to 11 down. Total: 99 blocks. Backing: 108 plus 8 is 116, divided by 36 is 3.22 yards per length. Width 90 plus 8 is 98 inches; at 42 usable inches per 44-inch fabric, that is 2.33, so 3 panels. Backing yardage: 3 times 3.22 is 9.67 yards, buy 10. Binding: perimeter is 396 inches, divided by 40 is 9.9, so 10 strips; 10 times 2.5 divided by 36 is 0.69 yards. Buy 10 yards of backing and three-quarters of a yard of binding.

Notice the backing width math: at 98 inches needed, two panels give only 84 usable inches, so the third panel is mandatory, not optional. Wide quilt backs exist, 108-inch wide fabric, and for a queen they are often cheaper than seaming three panels of 44-inch. Price both before you buy.

Pre-Cuts vs. Yardage

Quilt shops sell fabric in pre-cut bundles with real names: charm packs are 5-inch squares, layer cakes are 10-inch squares, jelly rolls are 2.5-inch strips, fat quarters are 18 by 22 inch cuts. Pre-cuts trade money for time: no cutting, coordinated fabrics, instant gratification. They cost more per yard than bolt yardage, sometimes double.

The math decides. A quilt needing 99 ten-inch blocks wants about three layer cakes, and at typical prices that rivals the cost of yardage plus your cutting time. For scrappy quilts with many fabrics, pre-cuts win on sanity. For quilts with one background fabric and one accent, yardage wins on price. Backing and binding almost always come from yardage; nobody backs a queen with charm packs. Buy pre-cuts for the fun, yardage for the foundation.

Common Quilt-Math Mistakes

First: finished versus unfinished block size. A "12-inch block" finishes at 12 inches but cuts at 12.5, because every seam eats a quarter inch per side. Designing in finished sizes and cutting in finished sizes produces a quilt that shrinks a half inch per block, compounding across the whole top. Second: forgetting the longarm allowance. Backing and batting need 4 extra inches per side; a backing cut exactly to the top size cannot be quilted on a longarm.

Third: not rounding block counts up. A 6.67-block row needs 7 blocks of fabric; the 0.67 does not discount itself. Fourth: binding strip math without seam loss. Forty usable inches per strip assumes you join them with diagonal seams; straight seams eat more. Fifth: buying exactly the calculated yardage. Fabric miscuts, pattern matching, and the occasional crooked cut are normal. The 10 percent safety margin is not pessimism; it is experience.