Definition
Grainline
The direction of the threads in a woven fabric. Lengthwise grain runs parallel to the selvedge and has the least stretch; crosswise grain runs across the width and gives slightly more; bias runs at 45 degrees and stretches the most.
Pattern pieces carry a grainline arrow that must be aligned with the lengthwise grain. Ignoring it is why a garment can twist around the body after a wash.
Tools that use this term
Fabric Calculator
Work out how much fabric to buy for a project from its finished size, the seam allowance you are cutting and the width of the bolt you are buying.
Fabric Yardage Calculator
Yardage from finished measurements for a garment, adding seam allowance, hem, layout waste and pattern repeat matching.
Curtain Fabric Calculator
Work out how much fabric curtains need from the window width, the fullness ratio, the drop and the pattern repeat.