How is the binding fabric calculated?

The perimeter is 2 × (width + height). An extra 10 inches is added for mitered corners. That total is divided by the usable strip length (fabric width minus a 0.5" seam allowance for joins) to get the strip count. Fabric needed = strips × strip width, converted to yards and rounded up to the nearest 1/8 yard.

A 2.5" strip gives approximately 1/4" of visible binding on each side of the quilt after folding in half and wrapping to the back — the most common finished width. Narrower strips (2.25") suit delicate work; wider strips (3"+) give a chunkier look or extra wearing durability on baby quilts.

What is WOF and why does it matter?

WOF stands for width of fabric — the measurement from selvage to selvage on the bolt. Most quilting cotton is 44–45" after pre-washing. Wide-back fabric can be 108". The calculator divides your required strip length by the usable WOF to count strips, so entering the correct WOF directly affects how many strips (and how much fabric) you need.

How is the backing yardage calculated?

The backing must be larger than the quilt top so it extends under the quilting frame. The calculator adds 4 inches on every side (8 inches total per dimension). It then works out how many panels of your fabric width are needed to cover that backing rectangle, choosing the panel orientation (vertical or horizontal seams) that uses the least fabric. Total yardage = panels × panel length, rounded up to the nearest 1/8 yard.

Why does the backing sometimes use vertical versus horizontal seams?

Rotating the panels can save significant fabric on long, narrow quilts. The calculator computes both orientations and automatically selects the more economical one. For a square quilt the saving is usually minimal; for a king-size bed quilt it can be half a yard or more.

Does this calculator cover wadding (batting)?

No — wadding is typically sold pre-cut to standard sizes (cot, twin, queen, king) or by the yard off a wide roll, and its size requirement is the same as the backing: quilt dimensions plus 4 inches per side. Use the backing dimensions displayed here when buying wadding yardage from a roll.

Quilt Binding & Backing Calculator

A quilt binding and backing calculator that tells you exactly how many strips to cut, how many panels to seam, and how many yards to buy — before you touch your rotary cutter. Enter your finished quilt size and fabric width and every figure updates instantly in your browser.

How it works

Binding

The binding wraps all four edges of the quilt, so the starting point is the perimeter:

Perimeter = 2 × (width + height)

Ten extra inches are added for the four mitered corners (roughly 2.5” of extra strip per corner). That gives the total strip length needed.

Each cross-grain strip is cut from selvage to selvage — one strip per row of fabric. Because each join loses about 0.5” in the seam allowance, the usable length per strip is:

Usable strip length = fabric width − 0.5”

Dividing the total strip length by the usable strip length and rounding up gives the strip count. The fabric requirement in yards is then:

Binding yards = (strip count × strip width) ÷ 36

rounded up to the nearest ⅛ yard, which is the smallest increment fabric shops cut.

Backing

The backing must extend beyond the quilt top on every side to stay taut in a longarm or domestic quilting frame. The calculator uses a 4-inch overhang per side (the standard most longarm quilters require):

Backing width = quilt width + 8” Backing height = quilt height + 8”

If a single panel of your fabric covers the backing width, no seams are needed. Otherwise the calculator works out how many panels are required in both orientations (vertical seams vs horizontal seams) and picks whichever uses less total fabric. The yardage is:

Backing yards = (panels × panel length) ÷ 36

again rounded up to the nearest ⅛ yard.

Worked example

Suppose you have a 60” × 80” throw quilt, using 44”-wide quilting cotton with 2.5”-wide binding strips:

Binding

Perimeter = 2 × (60 + 80) = 280 inches
Add corner allowance: 280 + 10 = 290 inches of strip needed
Usable strip length = 44 − 0.5 = 43.5”
Strips needed = ⌈290 ÷ 43.5⌉ = 7 strips
Fabric = 7 × 2.5” = 17.5” = 0.486 yd → rounded up to ½ yd

Backing

Backing size = (60 + 8) × (80 + 8) = 68” × 88”
Panels for vertical seams: ⌈68 ÷ 43.5⌉ = 2 panels × 88” = 176” = 4.89 yd
Panels for horizontal seams: ⌈88 ÷ 43.5⌉ = 3 panels × 68” = 204” = 5.67 yd
Vertical seams win → 2 panels, 1 seam, ≈ 5 yd (rounded to nearest ⅛)

Quilt size	Strip width	WOF	Binding	Backing panels	Backing fabric
40” × 40”	2.5”	44”	⅜ yd	2	2¾ yd
60” × 80”	2.5”	44”	½ yd	2	5 yd
90” × 108”	2.5”	44”	¾ yd	3	8¼ yd
90” × 108”	2.5”	108”	⅜ yd	1 (no seam)	3¼ yd

Using 108”-wide wide-back fabric on a king quilt cuts the backing to a single panel with no seams — a big time saver.

A note on grain and joining strips

Binding strips are normally cut cross-grain (selvage to selvage) and joined at 45° on the bias. The bias join spreads the bulk so no single point has four layers of seam. Press the whole length in half lengthwise (wrong sides together) before attaching. For curved or scalloped edges, bias-cut strips (cut at 45°) handle curves without puckering — they require about 15% more fabric.

All figures calculated here use cross-grain strips. If you are bias-cutting, add roughly 15% to the binding yardage shown and round up again.