Quilt Backing Calculator
Find out how much backing fabric to buy, including the overhang and the seam if your backing needs to be pieced.
Tip: use URL parameters to pre-fill, e.g. ?quiltWidth=72&quiltLength=90.
How the backing calculation works
Your backing fabric needs to be larger than your quilt top on every side so the quilter has room to work — and so the backing doesn't pull out from under the needle. A common allowance is 4 inches per side (8 inches total in each direction).
Step 1: add overhang. Add 2 × overhang to both the width and the length. For a 60" × 80" quilt with 4" per side, the backing needs to be at least 68" × 88".
Step 2: check the fabric width. Standard quilt-shop fabric is about 44" wide, with roughly 42" of usable width after the selvedges. If your required backing width fits in one panel, you buy one length. If not, you piece two or more panels side by side.
Step 3: calculate yardage. Multiply the number of panels by the length of the backing in inches, then divide by 36. With two panels, each 88" long, that's 2 × 88 = 176 inches, or about 4.9 yards.
This calculator assumes a plain seam between panels. If you're using 108" wide backing fabric, simply set the backing width to 108 and you'll usually need just one panel.
What each input means
- Quilt width and length (inches) — the dimensions of your finished quilt top. If your top isn't square, enter the width and length as measured.
- Backing fabric width (usable) — the width you can actually piece, after trimming selvedges. Standard quilting cotton is about 42" usable; wideback fabric is 108".
- Overhang per side (inches) — how much backing extends beyond the top on each side. Four inches is the standard minimum for machine quilting.
When to use it. Use this calculator before every backing purchase. It answers the three questions that determine your order: how large the backing rectangle must be, whether one fabric width is enough, and how many yards to buy. That's especially important for bed quilts, where backing is often the single largest yardage purchase in the project. If you're sending the quilt to a long-arm quilter, ask for their preferred overhang first and adjust the field before you calculate. When in doubt between two sizes, buy the larger one — leftover backing can always be trimmed or saved for another project.
Common mistakes to avoid
- Buying backing the same size as the quilt top. Without overhang, the backing pulls out from under the needle and the binding has nothing to grab.
- Using the nominal 44" width. Selvedges are unusable and should be trimmed before seaming, so count on about 42" usable.
- Forgetting to trim selvedges before piecing. Selvedges are tightly woven and can pucker, making the backing seam ripple after quilting.
- Ignoring pattern matching. A directional or large-scale print needs extra yardage so the pattern continues across the seam.
- Not asking your quilter first. Long-arm quilters often request 4-8 inches per side; check their requirements before you buy.
Frequently asked questions
How much overhang should I leave on quilt backing?
Four inches per side (8 inches total) is the standard recommendation for machine quilting. Long-arm quilters often ask for more. If you're unsure, more is safer than less.
Do I really need to piece my backing?
Only if your quilt is wider than your fabric. For a 44" wide fabric and a 68" wide backing, yes — you'll piece two panels. Wide backing fabric (108") is a convenient alternative that avoids the seam.
Should the backing seam run horizontally or vertically?
Either works. Many quilters run it horizontally so the seam falls along the quilt's width. Trim the selvedges before seaming so the seam lies flat.
What if I'm using a patterned backing?
Add extra yardage for pattern matching across the seam — usually 10–20% more. This calculator gives a plain-fabric estimate.