How to Calculate Quilt Backing Fabric: Yardage + Panel Guide
Updated: May 27, 2026
Why Backing is Calculated Separately
The backing formula uses panel counts (not area), because you buy yardage in full lengths and sew them together side by side — not as a single sheet. The calculation depends on your fabric width and whether you prefer vertical or horizontal seams.
Step 1: Add Overhang to Quilt Dimensions
Add 4” to each side of the quilt for the longarm quilting frame to grip and for trimming after quilting.
Backing width = quilt width + 8" (4" × 2 sides)
Backing length = quilt length + 8"Example: Queen quilt 90” × 108”:
Backing width = 90 + 8 = 98"
Backing length = 108 + 8 = 116"Step 2: Determine Number of Panels
Divide the backing width by the usable fabric width, rounding up.
Panels = ⌈backing width ÷ usable fabric width⌉Usable width after selvage removal:
- 44” fabric → 42” usable
- 42” fabric → 40” usable
- 60” fabric → 58” usable
- 108” fabric → 106” usable
For the queen example with 44” WOF:
Panels = ⌈98 ÷ 42⌉ = ⌈2.33⌉ = 3 panels| Quilt Width | 44” WOF (42” usable) | 60” (58” usable) | 108” (106” usable) |
|---|---|---|---|
| Baby 36” → 44” backing | 2 panels | 1 panel | 1 panel |
| Lap 50” → 58” | 2 panels | 1 panel | 1 panel |
| Twin 60” → 68” | 2 panels | 2 panels | 1 panel |
| Full 78” → 86” | 3 panels | 2 panels | 1 panel |
| Queen 90” → 98” | 3 panels | 2 panels | 1 panel |
| King 108” → 116” | 3 panels | 2 panels | 2 panels |
Step 3: Calculate Total Yards
Multiply panels by backing length (in inches), then divide by 36.
Total backing yards = (panels × backing length) ÷ 36Queen example:
(3 × 116) ÷ 36 = 348 ÷ 36 = 9.67 → buy 9¾ yardsFull Backing Yardage Reference
44” WOF Fabric
| Quilt Size | Backing Size | Panels | Yards |
|---|---|---|---|
| Baby 36×45” | 44×53” | 2 | 3.0 |
| Lap 50×65” | 58×73” | 2 | 4.25 |
| Twin 60×90” | 68×98” | 2 | 5.5 |
| Full 78×90” | 86×98” | 3 | 8.25 |
| Queen 90×108” | 98×116” | 3 | 9.75 |
| King 108×108” | 116×116” | 3 | 9.75 |
108” Wide Backing Fabric
| Quilt Size | Panels | Yards |
|---|---|---|
| Baby 36×45” | 1 | 1.5 |
| Lap 50×65” | 1 | 2.125 |
| Twin 60×90” | 1 | 2.75 |
| Queen 90×108” | 1 | 3.25 |
| King 108×108” | 2 | 6.5 |
Vertical vs. Horizontal Seams
Vertical seams (most common)
Panels run the full length of the quilt. Seams are parallel to the quilt length. Most efficient for standard WOF fabric.
Formula: panels × (quilt length + 8”) ÷ 36
Horizontal seams
Panels run the full width of the quilt. Used when the quilt is wider than it is long (landscape orientation) or to reduce total yardage on certain sizes.
Formula: panels × (quilt width + 8”) ÷ 36
- Where panels = ⌈(quilt length + 8”) ÷ usable fabric width⌉
For king quilts (108”×108”), horizontal and vertical seam methods use the same total yardage. Choose the orientation that best hides seams or matches the backing fabric print direction.
Sewing the Backing Panels
- Remove selvages — trim ½”–1” from each selvage edge before sewing.
- Sew panels together — use a ½” seam, pressed open or to one side.
- Press seams — pressing open reduces bulk and lays flatter.
- Trim to size — after quilting, trim backing to quilt + 1” on each side (or as required by your longarm quilter).
Use the Quilt Fabric Calculator Backing tab — select fabric width and enter quilt dimensions.
See also: Quilt Yardage Formula and How to Calculate Quilt Binding.