The short answer: measure your finished quilt top, add four inches to every side (eight inches if a longarm quilter is finishing it), and buy enough 108 inch wide backing to cover both of those numbers. The longer answer, with a chart, is below.
Why the margin matters
A backing is always cut larger than the top. The extra fabric gives you something to pin or baste to, it absorbs the small amount of drift that happens as three layers are quilted together, and it gives the longarm clamps something to hold. Four inches on every side is the minimum for domestic machine quilting. Most longarm quilters ask for six to eight inches on every side, and it is worth emailing yours before you cut rather than after.
So a finished top of 70 by 90 inches needs a backing of at least 78 by 98 inches for home quilting, or 86 by 106 inches for a longarm.
Quilt backing size chart for 108 inch fabric
Our fabric is 108 inches wide, so the width almost always takes care of itself. What you are really buying is length. One yard is 36 inches, so a 3-yard package is 108 by 108 inches.
| Quilt | Typical top size | Backing needed (4 in margin) | Order from 108 in fabric |
|---|---|---|---|
| Crib / baby | 36 x 52 in | 44 x 60 in | 2 yards |
| Throw / lap | 50 x 65 in | 58 x 73 in | 2.25 yards |
| Twin | 70 x 90 in | 78 x 98 in | 3 yards |
| Full / double | 84 x 90 in | 92 x 98 in | 3 yards |
| Queen | 90 x 108 in | 98 x 116 in | 3.5 yards |
| King | 104 x 94 in | 112 x 102 in | 3.5 yards |
Add half a yard to each of these if your quilt is going to a longarm quilter.
Where 108 inch fabric runs out
There is one limit worth knowing. The fabric is 108 inches wide, so no single cut can cover a backing dimension larger than 108 inches. A square king top of 108 by 108 inches needs a backing of 116 by 116 inches, and that will not come from one width no matter how much length you buy. For a top that large you either piece two lengths together or use a 120 inch backing.
Most king patterns finish nearer 104 by 94 inches, which fits comfortably: the 108 inch width covers the 102 inch dimension, and 3.5 yards covers the 112 inch dimension.
Turning the fabric
Because 108 inch fabric is wider than it is usually long on the bolt, you can run the width in whichever direction suits the quilt. For a queen top that measures 90 by 108 inches, the 108 inch fabric width covers the 98 inch backing dimension, and the 116 inch dimension comes out of the length. Work out which of your two backing numbers is under 108 inches, let the fabric width cover that one, and buy length for the other.
Ready to choose a backing?
Browse the full range of 108 inch quilt backing fabric, or start from the colour your quilt needs: blue, green, red and pink, purple, black and gray, brown or off white and cream.
Still not sure? Email sharon@108quiltbackings.com with the finished measurements of your top and we will tell you what to order.