How wide should quilt borders be?

A common guideline is to make the border width proportional to the block size. Try 1/4 to 1/3 of the block size. For 30cm blocks, borders of 7.5-10cm work well. Multiple borders often alternate narrow and wide.

Should I cut borders on the lengthwise grain?

Lengthwise grain (parallel to selvedge) is more stable and resists stretching. This is ideal for long borders. Cross-grain borders may need to be pieced but use less fabric. This calculator allows for cross-grain cutting.

How do I prevent wavy borders?

Measure the quilt through the centre, not along the edges. Cut borders to the centre measurement. Pin the border to the quilt, easing any fullness. Sew sides first, then top and bottom (or vice versa consistently).

What are mitered border corners?

Mitered corners meet at a 45-degree angle like a picture frame. They require longer border strips (add 2x the border width + 5cm to each strip). They look polished but use more fabric than butted corners.

SewCalcs

Border Calculator — Quilt Border Fabric

Calculate fabric needed for single or multiple quilt borders.

Quilt Width

Quilt Length

Border Width (finished)

Number of Borders

Seam Allowance

Fabric Width

Fabric Price (optional)

How We Calculate This

The calculator determines fabric needed for borders that wrap around all four sides of the quilt. Multiple borders are calculated iteratively as each border increases the quilt dimensions.

The formula

Final width = Quilt width + (Border width × 2 × Number of borders)

Final length = Quilt length + (Border width × 2 × Number of borders)

Fabric needed = Strip rows × Longest side length

Frequently Asked Questions

Related Calculators

Quilt Size Calculator

Calculate quilt dimensions for standard bed sizes with drop allowances.

Quilt Binding Calculator

Calculate binding strip fabric and length for finishing quilts.

Quilt Backing Calculator

Work out backing fabric needed with seaming for wide quilts.

Quilt Block Calculator

Calculate number of blocks and fabric for a quilt layout.

Strip Piecing Calculator

Calculate strip quantities for strip-pieced quilt blocks and designs.

Last updated: February 2026

All calculations are estimates. Always verify quantities before cutting or purchasing fabric.