Quilt Calculators is a small, independent site with free calculators for the last steps of making a quilt: borders, backing, batting and binding. It is built and maintained by a software developer who got tired of re-typing the same measurements into four different calculators, and of tools that only show one way to piece a backing.
The site is free to use and needs no account. Your measurements stay in your browser: they are not sent to us or stored on a server.
How we calculate
Every calculator uses the standard methods quilters use when working out fabric by hand. The defaults, which you can change on each calculator, are:
- Fabric width: 42" usable for 44/45" quilting cotton with selvages removed; 40" when cutting strips that get joined (binding, borders); 106" usable for 108" wide backing.
- Backing and batting: 4" extra on each side of the quilt, the usual longarm requirement.
- Backing seams: 1/2" seam allowance, so each seam uses 1" of width.
- Diagonal backing: fabric length = backing length × fabric width ÷ (2 × fabric width − backing width), with the seam allowance added across the slanted seam.
- Binding: perimeter + 12" for corners and joins; standard strip width 2 1/2".
- Borders: cut width = finished width + 1/2"; mitered strips get 2 × border width + 4" extra.
- Rounding: fabric to buy is rounded up to the next 1/8 yard, the smallest cut most shops sell.
Results are estimates. Shrinkage, directional prints, cutting mistakes and your quilter's requirements can all change what you need, so it's sensible to buy a little extra.
Found a mistake?
If a result looks wrong or you'd like a calculator we don't have yet, please get in touch. Corrections are fixed quickly and noted on the page.