Article — Fabric Calculator
Fabric calculator: how much fabric do you need for your project
A 48 in wide, 84 in tall curtain panel on 45 in quilting cotton needs about 4.5 yards once seam allowance, a 12 in pattern repeat and 5% shrinkage are folded in. Switch to a 54 in decorator bolt and the requirement drops to about 2.75 yards. The fabric calculator above handles the arithmetic — including pattern matching and bolt-width logic — and rounds up to the quarter-yard increment used at every cut counter.
Bolt width is the variable most beginners overlook. Pattern repeat is the variable that bites once you start cutting. Both are baked into the formula below, alongside seam allowance and a shrinkage buffer for natural fibres.
How the fabric calculator works
Fabric is sold off a rolled bolt with a fixed width. To work out how much length to buy, the calculator first adds seam allowance to the finished dimensions, then checks whether the project width fits across one bolt or needs two side-by-side widths.
length = finished + 2 × seamwidths = ceil(width / bolt width)yards = length × widths / 36If the fabric has a pattern repeat — a stripe interval, a flower motif, a plaid block — one full repeat is added so the pattern can be matched across seams. Shrinkage adds a percentage buffer on top. The final figure rounds up to the nearest 0.25 yard because fabric stores cut to that increment.
The 45 in standard for quilting cotton dates to mid-19th century power looms in Lancashire mill towns. The 36 in inch-per-yard ratio is older still — derived from the iron yardstick standardised by King Edward I of England in 1305. Modern weaving could produce almost any width, but the 45 in and 54 in standards persisted because every sewing pattern, fabric calculator and fabric-store cutting table is built around them.
Fabric yardage by project
Typical yardage requirements for standard project sizes on 45 in fabric, assuming basic seams and no pattern matching:
- standard pillowcase (20 x 26) = 1 yard
- euro pillow sham (26 x 26) = 1.5 yards
- tablecloth (60 x 60) = 2 yards
- tablecloth (72 x 108) = 3.5 yards
- simple A-line skirt = 2 yards
- simple dress (adult) = 2.5 yards
- quilt throw (48 x 60) = 3.5 yards
- curtain panel (48 x 84) = 4.5 yards
- upholstery chair (full) = 5-7 yards
Switching to 54 in or 60 in fabric reduces these figures noticeably for wide projects. A 48 in curtain panel needs two widths of 45 in cotton (4.5 yards) but only one width of 54 in decorator (2.75 yards) — saving nearly 40% in total fabric. The arithmetic favours wider bolts for anything over 45 in wide.
Standard fabric bolt widths
Four bolt widths cover almost every fabric type stocked in mainstream stores.
45 in (114 cm) quilting cotton is the most common width — cheap, available in thousands of prints, ideal for patchwork, lightweight garments and small home projects. 54 in (137 cm) suits decorator fabrics and dressmaking. 60 in (152 cm) covers fleece, denim and most home-décor weaves. 72 in (183 cm) and above are reserved for upholstery, sheeting and oversized projects where a single uninterrupted width is essential.
Seam allowance and shrinkage
Two buffers sit between finished dimensions and the yardage you actually order.
Seam allowance. Every cut edge needs extra fabric to fold under and stitch. Standard allowances: 0.5 in for pillowcases and quilting; 0.75 in for skirts; 1 in for upholstery and tablecloths; 1.5 in for curtain hems and casings. The calculator adds the allowance to every side, so a 1.5 in seam adds 3 in to both length and width.
Shrinkage. Natural fibres shrink on the first wash. Cotton and linen typically shrink 3-5%; wool can shrink 5-10%; pre-shrunk and sanforised cotton (most quilting cotton) shrinks only 1-3%. Synthetics shrink 0-2%. The shrinkage field adds a percentage buffer to the final yardage. For washable garments and curtains, leave the buffer in. For non-laundered upholstery, set shrinkage to 0%.
Pattern repeat fabric rules
A pattern repeat is the vertical distance over which the fabric design repeats — typically 4-24 in for prints, 1-3 in for simple stripes, 6-12 in for plaids. When two panels meet at a seam, the pattern needs to line up across the join. That requires extra length.
The calculator rounds working length up to the nearest pattern repeat, then adds one extra repeat as a matching allowance. Skipping this step is the single most common cause of running short on fabric. A 12 in repeat on an 84 in curtain panel adds 12-24 in of length — almost half a yard. Buy it. Pattern-matching mistakes can’t be fixed without a fresh cut.
Pattern matching matters for curtains and drapes (always), upholstery (always), tablecloths (sometimes), wallpaper-style installations (always) and dressmaking with large prints (sometimes). For abstract or random prints with no obvious vertical alignment, set the repeat field to 0 and skip the allowance.
Yards to meters conversion
The calculator outputs both units because fabric is sold by the yard in the United States and Canada and by the metre almost everywhere else.
One yard equals exactly 0.9144 metres. A quick mental rule: 1 yard ≈ 1 metre, within 8.5%. So 5 yards = 4.572 m, 10 yards = 9.144 m. For most projects, the difference between rounding up to the next yard versus next metre is negligible — about 3 in either direction. When ordering from a European or Japanese fabric shop, convert your yardage to metres and round up to the nearest 10 cm increment.
Yards to metres: multiply by 0.9. Metres to yards: multiply by 1.1. These approximations are accurate to within 1.5% — close enough for fabric buying, where you round up to the next quarter-yard or 10 cm anyway.
Common fabric buying mistakes
Five errors account for most "I ran out of fabric" moments.
Forgetting bolt width. If the project is wider than the bolt, you need two widths side by side. Buying only enough for one width leaves the project short by half the width.
Skipping pattern repeat. Patterned fabric needs a full repeat extra for matching. Without it, the pattern jumps at every seam.
Ignoring shrinkage. Cotton curtains that fit perfectly on Day 1 hang 3 in short after the first wash. Pre-wash before cutting, or build the buffer into the order.
Missing seam allowance. Finished dimensions are not cut dimensions. Add at least 0.5 in to every side, more for hems and casings.
Buying the minimum. Fabric stores sometimes can’t restock the same dye lot. Order half a yard extra on important projects — re-cutting a single panel is cheaper than re-doing the whole job.