How underwear is made

On a one-piece knitting line, two pairs of underwear come out as one tube, then an overlock machine splits them.

stations: 9
things upstream: 52
raw sources: 17
steps from the ground: 8

The short version

Cut-and-sew remains the widest route: knit cloth is dyed, dried, stacked and sliced into panels, then stitched together and joined to a separately knit elastic waistband. One-piece knit styles skip most of that, since a circular knitting machine makes the garment shape directly and only the crotch and leg openings need an overlock stitch. Tags and printed labels go on near the end.

Knit the cloth

Yarn goes onto knitting machines and comes off as stretchy cloth, with elastic fiber running through it. A one-piece knit line runs high-speed circular machines instead, and one attendant can watch 5 or 6 of them.

Goes in
Cotton yarn Nylon Polyurethane Spandex
Dye and dry

The cloth is dyed and dried before it moves to the sewing unit. One-piece tubes are knit from white yarn and take their color in a dyeing machine afterward.
Cut the panels

Industrial fabric cutters slice panels for each size out of the cloth. One-piece production drops this step altogether, which also saves fabric.
Knit the waistbands

Elastic waistbands are knit as a separate job while the panels are prepared. A one-piece tube builds a two-layer waistband straight into the knit.

Goes in
Polyurethane Spandex
Stitch the panels

Production lines sew the panels into a garment from the approved pattern, with checks along the way. A one-piece pair needs far less: an overlock machine separates the two pairs in a tube, closes the crotch and finishes the leg openings.

Goes in
Sewing thread
Join the waistband

A sewing machine fastens the sewn body to its waistband. Stray threads are trimmed off once the garment is together.

Goes in
Sewing thread
Print and tag

Fabric printers add any pattern, and each pair gets its brand and size. One such factory pad-prints size, care and fiber details inside the back, a method that needs no drying or curing.

Goes in
Ink
Check the stretch

Inspectors look at stitching, elasticity, seam strength and fit. One-piece garments are also checked under a light table after dyeing, so that knitting and color faults never reach the sewing station.
Pack in combos

Finished pairs are tagged and packed for shipping. One factory bundles 3 to 5 pairs of the same size in different colors.

End of the lineUnderwear

Worth repeating

A one-piece knit line can take underwear from knitting to packing within a single day.
Underwear makers often set higher minimum orders than T-shirt makers, because each pair uses so little fabric.
Boxer shorts take their name from the loose elastic-waist trunks designed for boxers in 1925, who needed unrestricted leg movement.