To cut fabric straight, first find the true straight grain by pulling a crosswise thread or following the selvage, square the cut end to it, then cut with the fabric lying completely flat on a table: along a ruler with a rotary cutter, or with long, closed scissor strokes while the lower blade stays on the table. A crooked cut almost always starts before the blade touches the fabric, with cloth that was off grain, stretched, or hanging over the edge of the table.

Why does fabric cut crooked?

Fabric is a grid of threads, and only the grid is straight: the raw edge from the shop was cut by someone in a hurry and can be off by several centimeters across the width. If you measure from that edge, every line you draw is tilted. The second cause is movement. Fabric that hangs off the table pulls itself downhill while you cut, and fabric that you lift with the scissors shifts under the upper blade. The third is the fabric itself: a woven cotton can be bowed or skewed by the finishing process, so that the crosswise threads curve, and knits twist around the tube they were made on.

Fixing the first two is habit; the third needs a quick check before you lay out the pattern.

What do you need to cut fabric straight?

  • A table you can walk around, at a comfortable height, bigger than the piece you are cutting. A dining table with a cutting mat is enough; a floor works for very large pieces, but cutting on carpet is harder.
  • A rotary cutter and a self-healing cutting mat, or a pair of sharp dressmaking shears that are used only for fabric. The rotary cutter vs scissors post compares them.
  • A long clear ruler, 60 cm (24 in) if possible, with a right-angle grid printed on it. A quilting ruler is ideal.
  • Pattern weights or pins, tailor's chalk or a washable marker.
  • An iron. Pressing the fabric flat before cutting removes folds that would otherwise be cut through at an angle.

How do you find the straight grain?

The straight grain runs parallel to the selvage, the tightly woven edge of the fabric, and the crosswise grain runs from selvage to selvage. Pattern pieces have a grainline arrow that must sit parallel to the selvage, so everything depends on knowing where that is.

On a woven fabric, there are two reliable methods for finding a straight crosswise line:

  • Pull a thread. Snip into the selvage near the raw end, tease out one crosswise thread with a pin, and pull it gently. The thread either comes out whole or breaks; either way it leaves a visible puckered line across the width. Cut along that line. This works on most cottons, linens and wools, and on loosely woven fabrics it is nearly foolproof.
  • Tear. Snip into the selvage 2 cm (3/4 in) and tear across in one quick motion. Quilting cottons, poplins and many lawns tear cleanly along a thread. Do not tear knits, silks, satins, loosely woven fabrics or anything that frays badly; it stretches the torn edge, and press that edge afterward even on fabrics that tear well.

On a knit, there are no threads to pull. Follow a single rib (a column of knit stitches) up the fabric with a pin or chalk; that is the straight grain. Cut the crosswise edge along one row of stitches, or square it with a ruler against a rib.

Once you have one straight crosswise edge, fold the fabric selvage to selvage and check that the crosswise cut edges meet evenly along their whole length while the fold lies flat. If the fold ripples or one edge hangs lower than the other, the fabric is off grain: pull the short corners gently on the diagonal, re-press, and check again. The laying out and cutting on grain guide covers this in more depth.

How do you cut fabric straight, step by step?

  1. Pre-wash and press if the fabric is washable. Shrinking happens unevenly along the two grains, so pre-washing before you square the end keeps the cut true after laundering.
  2. Square the cut end by pulling a thread or tearing, as above, then press the fabric flat on the table.
  3. Lay it flat with nothing hanging off. Fold or roll the excess onto the table rather than letting it drape over the edge. The weight of an overhanging meter of denim is enough to pull a straight line into a curve.
  4. Line the ruler up on the grain. Place one gridline of the ruler along the selvage or a pulled thread, and the cutting edge of the ruler where you want to cut. For a cut parallel to the selvage, measure from the selvage at both ends of the ruler and check that the two measurements are equal, say 30 cm (11 3/4 in) at each end, before cutting.
  5. Cut. With a rotary cutter, press the ruler down with spread fingers, keep the blade against the ruler's edge and push away from you in one smooth pass; move your hand down the ruler as you go on long cuts. With shears, keep the lower blade flat on the table, take long strokes and never close the blades completely: the last centimeter of a stroke is where a nick or a jog happens.
  6. Do not lift the fabric. Walk around the table instead of turning the cloth, and support the pattern piece with your free hand resting flat on it, not pinching it.
  7. Check your line against the ruler before moving on. A cut that is 3 mm (1/8 in) off on a waistband is harmless; on a long seam it adds up.
Tip: On a slippery fabric, lay a cotton sheet or a length of muslin on the table first. The fabric grips it and stays put while you cut.

How do you cut pattern pieces straight along the grainline?

Cutting around a pattern piece is cutting straight in disguise: the piece must be on grain before you cut, or the garment twists when worn. Measure from each end of the grainline arrow to the selvage and move the piece until the two distances are the same. Pin or weight it there. For a piece placed on the fold, the fold line of the pattern goes exactly on the fabric fold, and the fold itself must be parallel to the selvage. Pattern weights hold the piece flat without distorting it; pins pull the layers slightly, so keep them inside the seam allowance and perpendicular to the edge. Cut with the same long strokes, pivoting the fabric only at corners, and cut the notches outward as small triangles rather than snipping into the seam allowance.

Common mistakes when cutting fabric

  • Measuring from the shop's cut edge instead of squaring it first.
  • Folding along a tilted line. Fold selvage to selvage and let the fold find itself; a fold forced to match an off-grain edge puts a diagonal crease through the piece.
  • Cutting with the fabric half off the table.
  • Using household scissors, or fabric shears that have been used on paper. Blunt blades chew the edge and push the fabric away from the cut.
  • Closing the blades fully at the end of each scissor stroke.
  • Cutting a double layer of a fabric that creeps, such as satin or a lightweight jersey, when a single layer would be more accurate. Trace the piece twice instead.
  • Rushing the knits. Knits distort as you handle them; let the fabric rest flat on the table for ten minutes before cutting so it returns to its relaxed state.

When should you tear fabric instead of cutting it?

Tearing gives a perfectly straight crosswise line on fabrics that allow it, and it is the fastest way to square up a length of quilting cotton, poplin or lawn, or to cut plain rectangles such as waistbands, ties, ruffles and the panels of a gathered skirt. It is a poor choice on anything stretchy, loosely woven, sheer or expensive, where pulling a thread gives the same line without the stretched edge. For every piece with a curve, cut; for straight rectangles on a cooperative cotton, tear, then press the torn edge flat before measuring from it.