Backing and Batting Calculator
Type your finished top size and get the backing yardage, how many widths to piece and which way the seams run, plus the smallest batting precut and what the same batt costs off the roll.
Type the finished width and height of your quilt top, or tap a bed size. The backing yardage, the piecing, and the batting all fill in as you type.
The overhang is the whole point
The single most common backing mistake is cutting it exactly the size of the top. Whatever way you quilt it, the three layers shift against each other as they go through, and a backing cut flush will pull off the edge before you are done. Backing and batting both need a margin all the way around, and the calculator builds in the standard 8″ total, about 4″ per side, before working out the yardage. It is fabric you trim off and can save for scrappy backs, not fabric you waste.
Questions people ask
Why is the backing bigger than my quilt?
Backing and batting both need to hang past the quilt top on every side. A longarm has to clamp the extra, and even hand or domestic-machine quilting drifts a little, so the layers need room to shift without the top running off the edge. The calculator adds 8″ total to each dimension, about 4″ per side, which is the standard longarm allowance. You trim the extra off before binding.
Which way should the seams run?
Whichever way buys less fabric, which the calculator works out for you. Standard fabric is only about 42″ wide, so a quilt wider than that has to be pieced, and the two panels can sit side by side (seams running top to bottom) or stack (seams running side to side). One of those almost always uses noticeably less yardage. The seams themselves don't matter to the quilt; they're on the back.
What is wide backing?
Extra-wide backing fabric comes on 90″ and 108″ bolts made specifically so a quilt back can be one clean panel with no piecing seam. It usually costs more per yard, but you buy far less of it and skip the seaming, so for a big quilt it often comes out even or cheaper, and it's less work. The calculator shows both so you can compare.
Precut batting or off the roll?
A precut package is graded by bed size and is the no-fuss choice when one fits. Off-the-roll batting is the same batting sold by the yard, usually cheaper per quilt and the only option once you pass a King, and it lets you cut exactly what you need. Batting joins are butted edge to edge and whip-stitched rather than seamed, so nothing is lost to a seam allowance if you do have to join two lengths.
Is this the same math as TideStitch?
Yes. The app's cut list sizes backing and batting the same way, including billing each backing join for the seam allowance it eats and picking the cheaper of the two panel layouts. This page assumes 42″ usable fabric, a ¼″ seam, and standard 90″ and 108″ rolls.