Fabric Width Converter

Why the amount changes with width

Pattern envelopes list fabric amounts for the widths the pattern company tested, usually 45" (115 cm) and 60" (150 cm). If your fabric is a different width, you need a different length, because the pattern pieces need roughly the same area of fabric either way. Narrower fabric means the pieces can't sit side by side, so they go one above another and use more length.

The converter works on that principle:

new length = pattern length × pattern width ÷ your width

So 2 yards of 45" fabric covers the same area as 2 × 45 ÷ 60 = 1.5 yards of 60" fabric. The calculator then adds a small margin (1/8 yd or 10 cm) for straightening the cut end and for shrinkage when you pre-wash, and rounds up to the way fabric is sold.

When the simple conversion isn't enough

Area is a good approximation, not a guarantee, because pattern pieces are odd shapes that don't tile perfectly. Be generous in these cases:

• Going narrower. Check that your widest piece fits across the fabric at all. A full skirt panel, a circle skirt or a wide trouser leg may simply not fit on 36" (90 cm) fabric, whatever length you buy.
• One-way designs and naps. If every piece has to point the same way (directional prints, velvet, corduroy, satin, and fur-like fabrics), pieces can't be turned upside down to nest together. Allow about 10% more.
• Large prints, plaids and stripes. Matching a repeat across seams can use an extra repeat's length per major piece. Measure the repeat and add it for each matched piece.
• Knits and fabrics that shrink. Linen, rayon and many cottons shrink when pre-washed, often several per cent. Buy a little extra and always wash before cutting.

Quick conversion chart

Rounded up to the nearest 1/8 yard, including the small margin. Read along a row: if your pattern asks for the amount in the 45" column, you need roughly the amounts shown for other widths.

Fabric widths are nominal. A "60 inch" bolt can be anything from 56" to 62" of usable width once you exclude the selvages. Measure your actual fabric before you rely on the narrower end of any estimate.