How to sew darts that lie flat

To sew a dart that lies flat, fold the fabric right sides together so the two dart legs sit exactly on top of each other, pin, and stitch in a straight line from the wide end at the edge to the tip, finishing the last 1 cm (3/8 in) almost parallel to the fold and running off the fabric right at the point. Do not backstitch at the tip: tie the threads in a knot. Then press the dart over a curved surface such as a tailor's ham.

What a dart does

A dart is a wedge of fabric folded out and stitched to turn a flat piece into a three-dimensional shape. Bust darts make room for the bust, waist darts on skirts take the fabric in from the hip to the waist, and double-pointed darts shape a dress or a top through the waist. The wide end, where the two legs start, is where the most fabric is taken out; the tip is where the shaping fades away.

On Sewly patterns, darts are placed from your measurements. The bust dart points toward your bust point and stops 2.5 cm (1 in) short of it, and skirt waist darts are sized from the difference between your waist and your hip. Front skirt darts run 7 to 10 cm (2 3/4 to 4 in) long and back darts 11 to 15 cm (4 1/4 to 6 in), depending on your waist-to-hip depth.

Kinds of darts

• Single-point darts start at an edge and end at a tip: bust darts from the side seam, waist darts on skirts and trousers, shoulder darts.
• Double-pointed darts, also called fisheye or contour darts, sit inside the piece and taper to a tip at both ends, from under the bust to the hip on a fitted dress. On the pattern they look like a narrow diamond with a dot at each end.

Mark the dart

1. Snip the notches where the legs meet the cutting line, 3 mm (1/8 in) deep. Sewly marks the legs of skirt and bust darts this way.
2. Push a pin through the dot at the tip and chalk its position on the wrong side of each layer.
3. Draw each leg with a ruler, from the snip at the edge to the tip. A drawn line makes the stitching much straighter than sewing by eye.

See transferring pattern markings for marking methods by fabric.

How to sew a single-point dart

1. Fold. With the fabric right sides together, fold through the middle of the dart so the two leg snips meet and the drawn legs lie exactly on top of each other. Push a pin through the tip on the top layer and check that it comes out at the tip on the bottom layer.
2. Pin. Pin along the leg line with the pins at right angles to it, heads toward the edge.
3. Start at the wide end. Set a straight stitch 2.5 mm long (about 10 stitches per inch). Start at the edge, backstitch two or three stitches, then sew along the line.
4. Taper onto the fold. Over the last 1 to 1.5 cm (3/8 to 5/8 in), the stitching should run almost parallel to the fold, only a thread or two from it. The last two or three stitches run right along the fold edge and off the fabric. If you like, shorten the stitch to 1.5 mm (about 16 per inch) for the last 1 cm; it secures the point without a lump.
5. Do not backstitch at the tip. Reverse stitches at the point make a hard knot of thread exactly where the fabric should fade out. Sew off the fabric, leave tails about 10 cm (4 in) long, and tie them together in a double knot close to the fabric. Trim to 1 cm (3/8 in).
6. Press flat. Press the dart as sewn, from the wide end toward the tip, stopping at the tip, to set the stitches.
7. Press into shape. Open the piece and press the dart over a tailor's ham or a tightly rolled towel, from the wrong side, so the area around the tip stays rounded.

How to sew a double-pointed dart

1. Mark both tips and the widest point (usually the waist) on both legs.
2. Fold through the center of the dart, right sides together, matching the marks.
3. Start at the widest point and sew toward one tip, tapering onto the fold as above. Tie off.
4. Turn the piece over, start again at the widest point, overlapping three or four stitches, and sew to the other tip. Tie off. Sewing from the middle out keeps both ends symmetrical.
5. Clip into the fold at the widest point, to within 3 mm (1/8 in) of the stitching, so the dart can follow the curve of the waist without pulling.
6. Press as for a single-point dart.

Which way do darts get pressed?

To slash a dart in heavy fabric, cut along its fold to within 1.5 cm (5/8 in) of the tip, press the two halves open, and press the point flat. Use the right heat for the fiber: about 200 °C (390 °F) with steam for cotton and linen, 150 °C (300 °F) with a press cloth for wool, silk and viscose, 110 °C (230 °F) for polyester.

Check that the darts match

Hold the two pieces of a pair together, right sides facing, and check that the darts sit on top of each other and end at the same height. Uneven darts show most on the front of a skirt. If one is off by more than 5 mm (1/4 in), unpick it and sew it again.

Common mistakes and fixes

• A bubble or dimple at the tip. The stitching curved inward or stopped away from the fold. Unpick the last 3 cm (1 1/4 in) and sew again in a straight line that tapers gently onto the fold.
• A pointed bump at the tip on the outside. The dart ends too close to the fullest part of the body, or it was not pressed over a curve. Press over a ham with steam; if the bump remains, shorten the dart by 1 to 2 cm (3/8 to 3/4 in).
• Darts in the wrong place on you. Bust darts pointing above or below the bust are a fit issue, not a sewing one. Move the tip on a toile first, then transfer the change to the pattern.
• Puckering along the legs. Tension too tight or stitch too short. Test on a folded scrap of the same fabric.
• The knot comes undone. Tie a double knot, or thread the tails into a hand needle and run them along the fold for 1 cm (3/8 in).

The first two or three darts are always the hardest. Sew a pair on a scrap before the real garment, especially on a fitted piece like the pencil skirt.