Input variables
| Variable | Meaning | Unit |
|---|---|---|
| w | Current quilt width | in |
| h | Current quilt height | in |
| b | Finished border width | in |
| s | Seam allowance | in |
| fw | Usable fabric width | in |
| join | Extra length for strip joins | in |
Equations
Cut strip width · in
cut = b+2*s
Total strip length with allowance · in
total = 2*h+2*(w+2*b)+join
Width-of-fabric strips · strips
strips = ceil(total/fw)
Fabric length · yd
yards = strips*cut/36
Finished width · in
neww = w+2*b
Finished height · in
newh = h+2*b
Notation
PI means π. ** means a power, sqrt means square root, and abs gives the absolute value. Trigonometric functions use radians. min and max select the smallest or largest argument.
ceil rounds upward, floor rounds downward, and round rounds to the nearest integer with halves toward positive infinity. roundup(value, step) rounds upward to the next multiple of the step; a zero step leaves the value unchanged.
Assumptions
- Measure the actual quilt through its center before cutting each border.
- These lengths use side borders first and do not describe mitered corners.
- The join allowance is user supplied and must cover your chosen joining method.
- Piecing strips may be necessary even when the total yardage is sufficient.
Precision and verification
The tool uses ordinary double-precision numeric arithmetic. Output is displayed to at most four decimal places; measurement precision is usually much lower. Check the worked examples, your project’s specifications, and a real sample before committing material.