Quilt math · Calculator
Sashing and cornerstones calculator
The quilt’s size with sashing between the blocks, the strips and cornerstones to cut, and the fabric to buy for them.
The short answer
For 4 × 5 blocks of 12″ with 2″ sashing, cut 31 strips 12½″ × 2½″ and 12 cornerstones 2½″. The top is 54″ × 68″ before borders, and the sashing takes ⅞ yd.
Work out yours
Free · no accountQuilt top 54″ × 68″ before borders
20 blocks
Cut 31, 3 from each 42″ strip: 11 strips 2½″ wide.
Cut 12, from 1 strip 2½″ wide.
And ¼ yd for the cornerstones. Each with a spare strip.
In Quarter Inch, choose Sashing and Cornerstones for any quilt: the strips and squares are drawn, cut and added to the yardage for you.
Start designing freeSame sums as the app: @quarterinch/cutting · strips across 42″ of fabric · a spare strip · up to the next ⅛ yd
Sashing size chart
The quilt top’s width with sashing, before borders, for 4 blocks across. Each cell is 4 blocks and 3 strips. For the length, use the blocks down.
| Block | 1″ sashing | 1½″ sashing | 2″ sashing | 2½″ sashing | 3″ sashing |
|---|---|---|---|---|---|
| 6″ | 27″ | 28½″ | 30″ | 31½″ | 33″ |
| 8″ | 35″ | 36½″ | 38″ | 39½″ | 41″ |
| 9″ | 39″ | 40½″ | 42″ | 43½″ | 45″ |
| 10″ | 43″ | 44½″ | 46″ | 47½″ | 49″ |
| 12″ | 51″ | 52½″ | 54″ | 55½″ | 57″ |
Cutting the strips
| Block | Each strip cut | From one 42″ strip |
|---|---|---|
| 6″ | 6½″ long | 6 |
| 8″ | 8½″ long | 4 |
| 9″ | 9½″ long | 4 |
| 10″ | 10½″ long | 4 |
| 12″ | 12½″ long | 3 |
How it’s worked out
Sashing is the strips between the blocks. Cornerstones are the small squares where the strips cross, often in a second fabric. Between 4 blocks across there are 3 strips, so:
- Width: blocks across × block + (blocks across − 1) × sashing. Down works the same way.
- Strips: one between each pair of blocks, each the block’s length and the sashing’s width, both plus ½″.
- Cornerstones: (across − 1) × (down − 1), each the sashing’s width plus ½″ square.
| Across: 4 × 12″ + 3 × 2″ | 54″ |
|---|---|
| Down: 5 × 12″ + 4 × 2″ | 68″ |
| Strips: 3 × 5 + 4 × 4, each cut | 31 × 12½″ × 2½″ |
| 3 to a 42″ strip, so strips 2½″ wide | 11 |
| Cornerstones: 3 × 4, each cut | 12 × 2½″ |
| Sashing fabric, with a spare strip, up to the next ⅛ yd | ⅞ yd |
Sewing it together
- Sew the blocks into rows with a sashing strip between each pair.
- Sew the sashing rows: a strip for each block, with a cornerstone between each pair.
- Join the block rows and sashing rows, pinning at every cornerstone so the strips line up across the quilt.
Measure your blocks first. Blocks should all measure 12½″ before you sew them in. If yours vary, cut the strips to your blocks’ real size, not the pattern’s: they keep the rows straight.
What changes the answer
- No cornerstones. Long strips across the whole row save seams, but they don’t line up as easily. Quarter Inch still cuts a square where they cross, in the sashing fabric.
- Sashing around the outside. A strip around the edge too is a narrow border. See quilt borders.
- The width of your fabric. Narrower fabric fits fewer strips across. Measure from selvage to selvage, less the selvages.
Questions
Short answers.
Something else? A real person replies.
hello@quarterinch.app
How do I calculate sashing for a quilt?
Width: blocks across × block size + (blocks across − 1) × sashing width. One strip between each pair of blocks, each the block’s size by the sashing’s width, both plus ½″.
How many cornerstones do I need?
(Blocks across − 1) × (blocks down − 1). For 4 × 5 blocks, 12.
How much fabric for sashing?
For 4 × 5 blocks of 12″ with 2″ sashing: 11 strips across the fabric, ⅞ yd with a spare strip.
How wide should sashing be?
A quarter to a sixth of the block is common: narrow sashing frames the blocks, wide sashing lets them float. Try a few widths in the calculator.