Quilt Sashing & Border Calculator
A seamless lengthwise border costs more only up to about 8 inches wide. Past the crossing it is both seamless and cheaper.
Sashing all round costs more than it sounds
Sashing between blocks needs one fewer strip than there are blocks. Sashing round the outside as well adds two strips in each direction, not one — and because the cornerstones are the product of the two strip counts, they jump much faster than either. A 4×5 layout goes from 12 cornerstones to 30.
Worth knowing before you cut, because cornerstones are the fiddliest small pieces in the quilt and two and a half times as many of them is a different afternoon. The quilt also grows: the same blocks go from 54×68″ to 58×72″.
A seamless border is not always the expensive one
The received wisdom is that cutting borders lengthwise avoids joins but costs more fabric. That is true for narrow borders and false for wide ones, and the reason is simple once you see it.
Crosswise cost is strips × border width, so it scales with how wide the border is. Lengthwise cost is just the length of the longest border — it does not depend on the width at all, as long as four strips still fit across the fabric. On a 66×90 quilt the lengthwise figure is 2.50 yards at a 1-inch border and still 2.50 yards at an 8-inch one, while crosswise climbs from 0.28 to 2.22. So they converge, and they cross.
| Quilt | Premium at 2″ | Premium at 8″ | Crosses at |
|---|---|---|---|
| 36×52″ | +1.11 yd | -0.33 yd | 6.5″ |
| 50×65″ | +1.36 yd | +0.06 yd | 8.5″ |
| 66×90″ | +1.94 yd | +0.28 yd | 9″ |
| 80×90″ | +1.94 yd | 0.00 yd | 8″ |
| 90×100″ | +2.11 yd | +0.28 yd | 9″ |
| 108×100″ | +2.44 yd | +0.78 yd | 9.5″ |
Below the crossing, the premium is the price of a seamless border and it is worth seeing as a number. Above it — anywhere past roughly seven to nine inches — the lengthwise border is both seamless and cheaper, and cutting it crosswise is the worse option twice over.
Notes
- Measure the quilt top before cutting borders. Not the arithmetic — the actual top, through the middle in both directions. Borders cut to the calculated size and eased onto a top that came out slightly different is how quilts get wavy edges.
- Side borders first, then top and bottom. The top and bottom have to span the quilt plus the two side borders already attached, which this accounts for.
- Very wide borders break the lengthwise saving. Below four strips across the fabric you need a second length, and the cost doubles. At a 42-inch usable width that happens past about 10½ inches.
- Sashing widths are finished sizes. Add the half inch of seam allowance when you cut — a 2-inch finished sash is cut 2½.
How to use
- Enter the block layout, block size and sashing width.
- Say whether the sashing goes round the outside as well.
- Add a border width to compare crosswise against lengthwise cutting.
- Measure the actual quilt top before cutting the borders.
Frequently asked questions
How many sashing strips do I need?
One fewer than the number of blocks in each direction if the sashing runs between blocks only. If it goes round the outside as well, that adds two more in each direction — not one, which is the count people get wrong.
How many cornerstones does sashing need?
The product of the two strip counts, which is why the number jumps so fast. A four-by-five layout needs 12 cornerstones with sashing between blocks and 30 with sashing all round — two and a half times as many of the fiddliest small pieces in the quilt.
Should I cut borders lengthwise or crosswise?
It depends on the border width, and the usual advice is only half right. Crosswise cost scales with the border width; lengthwise cost does not, because it is just the length of the longest border. So the two converge, and somewhere around seven to nine inches they cross — past that a lengthwise border is both seamless and cheaper.
Is a lengthwise border always more expensive?
No. For narrow borders yes, and the premium can be a yard and a half. But on a 66 by 90 quilt the lengthwise figure is 2.50 yards whether the border is one inch or eight, while the crosswise figure climbs from 0.28 to 2.22. Past the crossing point the seamless option is also the cheaper one.
Why do the top and bottom borders need to be longer?
Because they span the quilt plus the two side borders already attached. Cutting all four the same length is a common way to end up two border-widths short, and the tool accounts for it.
How wide should I cut sashing?
The finished width plus half an inch for the two seam allowances, so a 2-inch finished sash is cut 2½. Every measurement in this tool is a finished size unless it says otherwise.
Why do my borders make the quilt wavy?
Almost always because they were cut to the calculated size and eased onto a top that came out slightly different. Measure the actual quilt top through the middle in both directions and cut the borders to that, not to the arithmetic.
Is there a limit to the lengthwise saving?
Yes. Below four strips across the fabric you need a second length and the cost doubles, which at a 42-inch usable width happens past about 10½ inches of border. Very wide borders go back to being expensive whichever way you cut them.
Does this send anything anywhere?
No. Everything is calculated in your browser and nothing is stored or uploaded.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.