Quilt fabric calculator

How to use the quilt calculator

1. Pick a size such as Throw or Queen, or type your finished quilt top measurements. Measure through the middle of the top in both directions, since edges can stretch.
2. Choose the width of your backing fabric. Standard quilting cotton is 42 or 44 inches. Wide backings come in 90, 108 and 118 inches.
3. Set how much extra backing you want around the edges. Four inches per side is the usual amount for home quilting.
4. Pick your binding strip width and, if your quilt has a plain outer border, its finished width.
5. Add a price per yard if you want a cost estimate, then download the project sheet to take to the store.

How the calculator works

The backing has to be larger than the quilt top so it can shift a little during quilting without leaving a bare edge. The calculator adds your overage to each side, then works out how many widths of fabric it takes to cover that area.

For standard-width fabric it subtracts 2 inches of selvage from the bolt width to get the usable width. It tries the panels both ways. Vertical seams mean the panels run the length of the quilt. Horizontal seams mean they run across it. Each option's yardage is the number of panels multiplied by the length of each panel. The calculator converts that to yards and rounds up to the next eighth of a yard, which is how most shops cut fabric.

Binding length is the distance around the quilt plus 12 inches for joining the strips and finishing the ends. That length divided by the usable fabric width gives the number of strips to cut. The calculator matches batting to the smallest common package that covers the backing size. Packaged sizes differ a little between brands, so check the label.

Formulas

• Backing size = (quilt width + 2 × overage) × (quilt length + 2 × overage).
• Panels = (backing dimension − 1) ÷ (usable fabric width − 1), rounded up, which allows ½ inch of seam allowance on each side of every seam.
• Backing yards = panels × panel length ÷ 36, rounded up to ⅛ yd.
• Binding strips = (2 × (width + length) + 12) ÷ usable width, rounded up.
• Binding yards = strips × strip width ÷ 36, rounded up to ⅛ yd.

Worked example: a queen quilt

Take a 90" × 95" queen top with 4 inches of overage. The backing needs to be 98" × 103". With 40 inches of usable fabric width, vertical seams need three panels 103 inches long, which is 309 inches or 8⅝ yards. Horizontal seams also need three panels, but each is only 98 inches long. That comes to 294 inches, or 8¼ yards, so horizontal seams save three eighths of a yard.

For binding, the distance around the quilt is 370 inches. Adding 12 inches gives 382, which takes ten 2½" strips cut across the fabric. Ten strips at 2½ inches is 25 inches of fabric, so buy ¾ yard. The backing needs to cover 98" × 103", which is too wide for queen batting (90" × 108"), so you need a king package.

Quilt backing and binding chart

Amounts below assume 4 inches of overage per side and 2½" binding strips. Your own measurements will give a more exact answer in the calculator above.

How much fabric for a quilt, by size

The calculator plans every fabric except the pieced top. This table adds a plain 4 inch border to each size, inside the finished measurements, with 42" backing and 2½" binding. The last column is a rough figure for a simple top. It uses the rule of thumb from Stitchin' Heaven's yardage guide. Divide the quilt's square feet by 9, since one yard of 44" fabric gives roughly 9 to 10 square feet.

The square-foot rule leaves out seam allowances, so a pieced top needs more. Stitchin' Heaven's own chart puts a simple to moderately pieced queen top at 7 to 8½ yards, while the rule gives 6⅝ yards. Small pieces lose more fabric to seams than big ones. For an exact top figure, list your pieces in the fabric yardage calculator. To find how many blocks fill each size, use the quilt layout calculator.

What changes the fabric total

• Backing width. Backing is the biggest single item. A queen needs 8¼ yards of 42" fabric but only 2¾ yards of 108" wide backing.
• Borders. A 4 inch border adds ¾ yard to a throw and 1¼ yards to a queen in the table above. Stitchin' Heaven estimates close to a full yard for a 4 inch border on a throw, so their figure includes a little more spare than ours.
• Shrinkage. Stitchin' Heaven says quilting cotton shrinks 3 to 5 percent when prewashed. On a 90" × 95" queen, 5 percent is about 4.5 inches of width and 4.8 inches of length. Missouri Star suggests buying about 5 percent extra backing if you prewash.
• Directional prints. You have to cut one-way prints the same way up every time, which wastes some fabric. Tick "Directional print" so the backing panels stay upright.
• Precuts. A charm pack holds about 42 five inch squares and a jelly roll about 40 strips 2½" wide, per Stitchin' Heaven. Precuts can make a whole top, but you still need yardage for the backing, binding and any border.

Tips before you buy

• Prewash or plan for shrinkage. Cotton can shrink a few percent, so if you prewash, buy a little extra.
• Wide backing saves seams on large quilts and often costs less per square inch than piecing several cuts of 42" fabric.
• Buy all your backing from the same bolt so the color matches across the seam.
• Trim selvages before sewing backing panels together. They shrink at a different rate and can pucker the seam.
• If you're near the end of a bolt, ask the store to measure it. Being a few inches short on a backing panel is hard to fix.