Quilt binding calculator

How much binding fabric do I need?

Enter the size of your finished quilt. You get the number of strips to cut across the width of fabric and how much fabric to buy for double-fold binding.

Your binding

7strips 2¹/₂″ wide, cut across the fabric
5/8 ydfabric to buy (0.5 m)
276″binding needed (7.67 yd)
264″perimeter of a 60″ × 72″ quilt

Strips across the width of fabric, selvage to selvage.

Cut 7 strips 2¹/₂″ × the width of fabric: 17¹/₂″ of fabric in all.
Joined end to end with diagonal seams they make about 279″ (708.7 cm) of binding, 3″ more than the 276″ you need (perimeter plus your extra for corners and the final join).
Each strip after the first adds about 39¹/₂″: the usable width less one strip width taken up by its diagonal join.
The amount to buy adds 2″ for straightening the cut edge, then rounds up to the next 1/8 yard.
Bias binding instead (for curved or scalloped edges): a square of about 29″ cut as continuous bias gives roughly the same length. This is an estimate, so make your square a little larger if in doubt.

How the binding is worked out

Measure the finished quilt after quilting and squaring up, not the pattern size. The binding has to go all the way round, so the starting point is the perimeter: twice the width plus twice the length. Add an extra allowance for the mitred corners and for joining the two ends: Missouri Star adds about 12″, Fat Quarter Shop 20″.

Strips are cut across the width of fabric, selvage to selvage, and joined with diagonal seams so the bulk spreads out. Each diagonal join uses up about one strip width, so every strip after the first adds the usable width minus the strip width. The calculator counts strips until they reach the length you need, then multiplies by the strip width to get the fabric.

Binding = 2 × (width + length) + extra.
Fabric = strips × strip width.

The amount to buy adds 2″ (5 cm) so you can straighten the cut edge, then rounds up to the next 1/8 yard or 10 cm. Quilt shops cut to those steps.

Worked example

A 60 × 72″ quilt has a 264″ perimeter; with 12″ extra you need 276″ of binding. Each 42″ strip of 2 1/2″ binding adds 39 1/2″ once joined, so seven strips give 279″. Seven strips × 2 1/2″ is 17 1/2″ of fabric; with 2″ for straightening, buy 5/8 yard.

Sources

Missouri Star Quilt Co., The ultimate quilt binding tutorial: measure all four sides and add about 12″, cut 2 1/2″ strips selvage to selvage, join them on the diagonal, about 40″ usable per strip.
Fat Quarter Shop, How to bind a quilt: perimeter plus 20″, divided by 40″ for the number of strips, multiplied by the 2 1/2″ strip width.
Cut Out + Keep, Quilt binding tutorial: strips from about 1 1/4″ for single-layer binding up to 2 3/4″ for double-layer binding.

Binding questions

What width should I cut binding strips?

For double-fold (French) binding, 2 1/2″ is the most common width. Narrower strips such as 2 1/4″ give a slimmer binding on quilts with thin batting; wider ones such as 2 3/4″ suit thick batting or a bolder edge. Make a short test piece if you are unsure.

Why join binding strips on the diagonal?

A 45-degree seam spreads the extra layers of seam allowance along the binding instead of stacking them in one spot, so the join does not make a lump when the binding is folded over the edge. It uses up roughly one strip width of length per join, which the calculator allows for.

Do I need bias binding?

Only for curved or scalloped edges, where the stretch of the bias lets the binding bend smoothly. Straight-grain binding cut across the width of fabric works well for straight edges and uses fabric more efficiently.

Can I use leftover backing fabric for binding?

Often, yes. When a backing is pieced from two or three widths there is usually a strip left over along one side. The backing calculator tells you how wide that leftover is, and you can cut it into binding strips running along its length.