Free Calculator
How Many 15-inch Blocks for a Full / Double Quilt?
A Full / Double quilt (80″ × 96″) needs 20 blocks with standard sashing, or 30 blocks set without sashing.
Your Block Count
2″ sashing · 3″ border
Finished: 72″ × 89″
No sashing or border
Finished: 75″ × 90″
Layout with Sashing (4 × 5)
Each square = one 15-inch block. Gray gaps represent 2″ sashing.
Estimated Fabric (with sashing + border)
Estimates assume a 2-color block, 2″ sashing, 3″ border, and standard 44″ quilting cotton. Add 10–15% for error.
Planning a Full / Double Quilt with 15-inch Blocks
A Full / Double quilt typically measures 80 × 96 inches finished —fits a full-size mattress with a decent side drop. Using 15-inch finished blocks with 2-inch sashing and a 3-inch border, you will need 20 blocks arranged in a 4 × 5 grid.
If you prefer a simpler layout without sashing — blocks set edge to edge — the same Full / Double quilt needs 30 blocks in a 5 × 6 arrangement, finishing at approximately75″ × 90″.
Choosing Your Sashing Width
Sashing frames individual blocks and brings the quilt top to the desired finished size with fewer blocks. Wider sashing (3–4 inches) gives a more open, airy feel; narrower sashing (1–1.5 inches) lets the blocks be the star. No sashing at all creates a seamless all-over pattern — especially effective with blocks that form continuous secondary designs when set edge to edge, like Pinwheel, Nine Patch, and Flying Geese.
Calculating Fabric for a Full / Double Quilt
The fabric estimates above assume two fabrics per block, standard 44-inch quilting cotton, and a seam allowance of ¼ inch. In practice, quilts made from many different scrappy fabrics will need different yardages for each fabric. Add 10–15% to all estimates to account for cutting waste, miscuts, and design changes.
For the backing, you will need the quilt top dimensions plus 4 inches on all sides. A Full / Double quilt top of approximately 72″ × 89″ needs a backing of at least 80″ × 97″. For quilts wider than 44 inches, backing fabric must be pieced or wide backing fabric (108 inches wide) used.