How to measure your quilt top
Measure through the center of the quilt top, not along the edges. Edges stretch while you piece and press, especially where seams end or blocks are cut on the bias, so an edge measurement is often longer than the middle. Borders cut to that longer number end up wavy.
Lay the top flat without pulling on it. Measure the length in three places: down the center and about a quarter of the way in from each side. Use the average, or the center measurement if the three are close. Do the same for the width. Enter the raw measurement, edge to edge; the calculator accounts for seam allowances itself.
Butted, mitered or cornerstone borders
Butted borders
The most common and simplest choice. You sew strips to the two sides first, then sew the top and bottom strips across the full width, covering the ends of the side strips. The top and bottom strips are longer than the quilt top's width by twice the border width. You can also do top and bottom first; the strip lengths just swap.
Mitered borders
The strips meet in a diagonal seam at each corner, like a picture frame. They suit stripes, border prints and multiple borders that you want to turn the corner neatly. Each strip has to run past the corner on both ends, so mitered borders take more fabric and a little more care to sew.
Cornerstone borders
All four strips are cut to the length or width of the quilt top, and a square (a cornerstone) is sewn to each end of the top and bottom strips. Cornerstones are a good place for a contrasting fabric or a small pieced block, and they make it easy to match the corners.
How the math works
The calculator works one border at a time, from the inside out. For each border:
- Cut width = finished border width + 2 × seam allowance.
- Butted: 2 side strips as long as the quilt's length; 2 top and bottom strips as long as the quilt's width + 2 × the finished border width.
- Mitered: every strip is the quilt edge + 2 × the cut width, plus any extra length you add for trimming the miter.
- Cornerstones: 2 side strips as long as the quilt's length, 2 top and bottom strips as long as its width, and 4 squares the size of the cut width.
- Crosswise strips: add up the four strip lengths, divide by the usable fabric width minus 2 × the seam allowance (the bit lost at each join), and round up. That's how many strips to cut. Fabric needed = number of strips × cut width.
- Lengthwise strips: count how many cut widths fit across your fabric. The fabric needs to be as long as the longest strip, or longer if the strips don't all fit side by side.
After each border, the quilt grows by twice that border's finished width in each direction, and the next border is sized from the new measurements. Fabric amounts are rounded up to the next 1/8 yard (or 0.1 m), a common cutting increment at quilt shops.
Worked example
A quilt top measures 60 1/2" × 72 1/2" through the center. You want one 4" finished butted border, cut crosswise from 40" usable-width fabric, with 1/4" seams.
- Cut width: 4" + 2 × 1/4" = 4 1/2".
- Side strips: 2 at 72 1/2" (the quilt's length).
- Top and bottom strips: 2 at 60 1/2" + 2 × 4" = 68 1/2".
- Total length: 72 1/2 + 72 1/2 + 68 1/2 + 68 1/2 = 282".
- Each 40" strip gives 39 1/2" once you allow for the join: 282 ÷ 39 1/2 = 7.14, so cut 8 strips.
- Fabric: 8 × 4 1/2" = 36", which is exactly 1 yard.
With the border on, the quilt measures 68 1/2" × 80 1/2" raw, or 68" × 80" finished after binding takes the outer 1/4" seam allowance.
Questions
Should I cut borders longer and trim them?
Many quilters cut a couple of inches extra and trim after pinning, which is a cheap safety margin if you're unsure of your measurements. Use the "Extra length per strip" field for that. Mitered borders always need extra so you have room to trim the miter.
Why do my borders ripple?
Usually because the strips were cut to the edge measurement instead of the center, or sewn on without pinning, which stretches the strip or the quilt edge as it goes under the needle. Cut to the center measurement, pin the ends and middle first, then ease the fullness in between.
Should I cut borders crosswise or lengthwise?
Crosswise strips (selvage to selvage) use the least fabric but need to be joined, and they have a little more stretch. Lengthwise strips are cut parallel to the selvage, stretch less and need no joins, but you have to buy fabric as long as your longest strip. Lengthwise is worth it for border prints, long borders, and fabric you'd like to show without seams.
How do multiple borders work?
Add a row for each border. The calculator sizes border 2 from the quilt with border 1 already on, and so on, and gives each border its own yardage because each is usually a different fabric. If you plan to sew several mitered borders into one band and miter them together, cut every strip in the band to the length shown for the outermost border.
Does it work in centimeters?
Yes. Switch the units at the top of the calculator. Your sizes are converted, and the defaults change to a 0.75 cm seam allowance, 102 cm usable fabric width and 5 cm extra for mitered borders. Fabric is given in meters, rounded up to the next 0.1 m.
About this calculator
This is a free tool for quilters planning borders, whether you're finishing your first quilt or adding a third border to a sampler. It does the arithmetic; your measurements and your pattern still come first, so if a pattern gives its own border sizes, check them against your actual quilt top before cutting.