Measurements you need
Tape horizontally across the most prominent points of the bust, at the back — slightly above the shoulder blades, under the arms. In your usual underwear, not pulled tight.Tape horizontally across the most prominent points of the bust, at the back — slightly above the shoulder blades, under the arms. In your usual underwear, not pulled tight.
Usually 31½–51⅛ in.Usually 80–130 cm.Tape horizontal around the narrowest part of your torso, usually ¾–1⅝ in above the navel. Snug but not tight; don't pull in your stomach.Tape horizontal around the narrowest part of your torso, usually 2–4 cm above the navel. Snug but not tight; don't pull in your stomach.
Usually 22⅞–43¼ in.Usually 58–110 cm.Tape horizontal around the fullest part of your buttocks, allowing for the curve of your stomach. Stand straight, feet together.Tape horizontal around the fullest part of your buttocks, allowing for the curve of your stomach. Stand straight, feet together.
Usually 33⅛–51⅛ in.Usually 84–130 cm.Tilt your head: a prominent vertebra can be felt at the base of the neck at the back. Tape from it down along the spine to the waist tape.Tilt your head: a prominent vertebra can be felt at the base of the neck at the back. Tape from it down along the spine to the waist tape.
Usually 14⅝–17⅜ in.Usually 37–44 cm.At the side, from the waistline down to the level where you measured the hip. It helps to tie a ribbon at the waist and measure from it.At the side, from the waistline down to the level where you measured the hip. It helps to tie a ribbon at the waist and measure from it.
Usually 7⅛–8⅝ in.Usually 18–22 cm.The key measurement for a one-piece swimsuit. Tape from the mid-shoulder down through the bust, between the legs and up the back to the same point on the shoulder. Stand straight, don't pull the tape tight. Without this measurement the pattern maker will estimate it from the back length and circumferences.The key measurement for a one-piece swimsuit. Tape from the mid-shoulder down through the bust, between the legs and up the back to the same point on the shoulder. Stand straight, don't pull the tape tight. Without this measurement the pattern maker will estimate it from the back length and circumferences.
Usually 55⅛–68⅞ in.Usually 140–175 cm.How the swimsuit is drafted
The width of the piece under the armhole, at the waist and at the hips is a quarter of the circumference multiplied by the fabric stretch factor: for swimwear lycra it's 0.85, so the swimsuit is 15% smaller than the body and fits snugly. The sides of the front and back are the same, but the front is longer by the difference between the front and back waist lengths: this gives room for the bust without darts. Lengthwise the fabric stretches less, so lengths are reduced by 5%. The front and back together make up the vertical torso circumference with this reduction; below the waist the length is divided between front and back as 42 : 58.
We checked the draft against proven commercial patterns of the same style: the main dimensions match.
The pattern maker checks the draft itself: circumferences under the armhole and at the waist, matching side and shoulder seams, the inseam width, the torso length and the leg opening. The results are in the "Draft check" section.
How to sew
Place the front on the lining and baste along the edges. Sew the shoulder seams, side seams and inseam — with an overlocker or a stretch stitch. Attach elastic along the neckline, armholes and leg openings, turn to the wrong side and topstitch with a zigzag.
How to print and tape
Download the PDF on Letter or A4 sheets and print at 100% scale, without "fit to page". The first sheet has the test square: measure it with a ruler. The sheets are taped together with an overlap along the strips ⅜ in1 cm; sheet numbers and the assembly diagram are on the first page. For a copy shop or plotter, choose "One-sheet PDF".
What you get
Front and back on the fold at full size, with seam allowances and hem allowance for the elastic. Cut the front twice: from the main fabric and from the lining.
FAQ
Why the vertical torso circumference?
This is the key measurement for a one-piece swimsuit: from the mid-shoulder through the bust, between the legs and along the back to the shoulder. If the swimsuit is shorter, it pulls on the shoulders and cuts in at the crotch; if longer, it wrinkles at the tummy. Without this measurement the pattern maker estimates it from back waist length, bust and hip, but it's better to take it: the estimate can be off by 1⅛–1⅝ in3–4 cm.
What fabric to choose?
Swimwear lycra (polyamide or polyester with 15–20% elastane) holds its shape in water and resists chlorine. The front is lined with a lining mesh or thin lycra — cut a second front piece. Stretch 3⅞ in10 cm of fabric across: up to 5⅛ in13 cm is low stretch, 13–16 medium, more is high stretch.
How much elastic do I need?
The pattern maker suggests it under the drawing: for the neckline and each armhole — about 0.9 of the edge length, for each leg — about 0.85 of the opening. Swimwear elastic ¼–⅜ in0.6–1 cm wide is sewn with a zigzag on the wrong side, stretching slightly, then turned under and topstitched. At the legs, stretch the elastic more at the back than at the front — this keeps the swimsuit from riding up.
How to choose the back and leg openings?
A closed back is for swimming, a classic back sits just below the shoulder blades, a low back goes almost to the waist. Leg openings: low covers the hips, classic is like most swimsuits, high lengthens the legs. If the leg opening comes out too tight, the pattern maker will raise it automatically.