There are few quilting heartbreaks quite like getting your quilt sandwiched, halfway pinned, and realizing the batting falls two inches short on one side. The good news is that it's completely avoidable once you know two things: the standard sizes batting comes in, and the simple rule for how much bigger than your quilt top it needs to be. Let's sort both out.
The standard packaged sizes
Pre-cut batting comes in packages sized to match common quilt and mattress dimensions. These are the sizes you'll find on the shelf, and the ones the Batting Size Calculator matches your quilt to automatically:
- Craft: 36 × 45 inches
- Crib: 45 × 60 inches
- Throw: 60 × 60 inches
- Twin: 72 × 90 inches
- Full / Double: 81 × 96 inches
- Queen: 90 × 108 inches
- King: 120 × 120 inches
Notice these are named after beds, not after quilts. That matters, because your quilt top is rarely the exact size of the mattress — and even when it is, you need batting bigger than the top, not equal to it. Which brings us to the rule that trips up most people.
Batting has to be bigger than your top
Your batting sits in the middle of the quilt sandwich, and it needs to extend past the quilt top on every side. This is non-negotiable: the layers shift as you quilt, and that margin is what keeps you from running out of batting before you run out of top.
How much margin? It depends on how you'll quilt it:
- Longarm quilting: about 4 inches of overhang on every side. Longarm frames need room to clamp and to handle the drift that happens as the quilt feeds through.
- Domestic (home) machine: 2 inches per side is fine, since you're managing the layers yourself.
The math is straightforward once you know it:
Rule of thumb: batting size = (quilt width + 2 × overhang) × (quilt length + 2 × overhang). For a longarm, that's your top plus 8 inches in each direction. For home machine, plus 4.
The overhang gets added to both sides, which is why you double it. A 4-inch overhang adds 8 inches total to the width and 8 to the length.
Then size up to the next package
Here's the step people skip: once you've added your overhang, you don't look for a package that matches that number — you look for the next size up. Packaged batting comes in fixed sizes, so unless your math lands exactly on a standard dimension, you round up. A batting that's a hair too big is trimmed in seconds; a batting that's a hair too small is a return trip to the shop.
A worked example
Say you've made a generous 60 × 72 throw and you're sending it to a longarmer. Add 4 inches of overhang on each side:
- Width: 60 + 4 + 4 = 68 inches
- Length: 72 + 4 + 4 = 80 inches
So you need batting at least 68 × 80. Scan the standard sizes: Throw (60 × 60) is too small, but Twin (72 × 90) comfortably covers 68 × 80 with room to spare. One Twin package and you're set — no piecing, no shortfall. (Quilting it at home instead? Two inches per side gives you 64 × 76, and the Twin still works.)
That "scan the list and round up" step is exactly what the Batting Size Calculator does for you — type in your top's measurements, tell it your overhang, and it returns both the cut size and the package to buy.
Package versus off the roll
Pre-cut packages are convenient, but they're not your only option. Quilt shops and online retailers also sell batting by the roll, in widths commonly running 90, 96, 108, and 120 inches. Off a roll, you buy only the length you need rather than a fixed rectangle — which makes it the smarter, cheaper choice for odd or in-between sizes.
Back to our 68 × 80 throw: rather than buy a full Twin package, you could cut 80 inches off a 96-inch-wide roll. The roll's 96-inch width easily covers your 68 inches, you pay only for the 80 inches of length, and you skip the waste of a package sized for a bed you're not making.
- Buy a package when: your quilt is close to a standard bed size, or you only make a quilt now and then
- Buy off the roll when: your quilt is an odd size, you quilt often, or you want to minimize waste and cost
The quick version
- Standard packages: Craft 36×45, Crib 45×60, Throw 60×60, Twin 72×90, Full/Double 81×96, Queen 90×108, King 120×120
- Add overhang first — 4 inches per side for longarm, 2 for home machine — then round up to the next package
- Off the roll (90"–120" wide) you buy only the length you need — better for odd sizes
- Let the Batting Size Calculator do the rounding so you never come up short
While you're sizing the middle layer, remember the bottom layer needs margin too. Your backing should keep pace with your batting — the backing overhang guide explains how much, or run the numbers in the Backing Yardage Calculator. And before you buy, a quick read of the batting types compared and batting loft guide makes sure you're buying the right kind in the right size.