Bra manufacturing is the factory sequence that turns lace, stretch net, foam, narrow elastic and trims such as wires, hooks and sliders into a finished bra. The style is designed and patterned, graded into a grid of band and cup sizes, and cut. The cups are either sewn from flat panels (cut-and-sew) or moulded from a sheet of polyurethane foam pressed between heated aluminium moulds at about 200 °C. The centre front, wings and cups are then sewn in a chain of short operations on zigzag, single-needle and twin-needle lockstitch and bartack machines; the underwires are slid into their channels at a hand table and bartacked in; the hook-and-eye tape and the straps are attached; and the cups, trims and elastics are checked and tested. In one 2025 factory study a wired, moulded bra carried 12.03 standard minutes of sewing work, against a stated target of 1,047 bras a day.
Last verified: 12 October 2026. The figures come from peer-reviewed studies of bra moulding, sizing and line balancing, from standards bodies’ catalogue entries, from a thread maker’s stitch table for bras and from a university thesis on moulded bras, all listed at the end. Where a figure describes one factory or one study, the text says so.
Bra manufacturing at a glance
| Stage | What happens | From the sources |
|---|---|---|
| Design and pattern | Flat pattern pieces for the cups, cradle, centre gore, wings and straps | Moving only the cup seamlines changed cup volume by up to 13–17% in one study |
| Sizing and grading | Each size is a band and a cup, so a range is a grid of sizes | EN 13402-3 defines cup size as bust girth minus underbust girth |
| Cutting | Lace, net, lining and laminate cut to the graded patterns | No bra-specific figure; the cutting room works as for other garments |
| Moulding (moulded styles) | Foam sheet pressed into a cup between hot male and female moulds | About 200 °C; dwell times of 60–180 seconds studied |
| Sewing | Centre panel, wings and cups made up, then joined | 22 operations itemised in one factory study |
| Wiring | Wire inserted at a hand table, then bartacked | Four operations, 1.99 standard minutes in that study |
| Trims | Hook-and-eye tape, straps, rings and sliders attached | Hooks and eyes on zigzag; straps bartacked to cup and back |
| Checks and tests | Moulded cups checked; elastics, fabrics and trims tested | ASTM D4964 for elastic; pull-off and slippage tests for trims |
The parts of a bra, what each is made of and how it is sewn
The underwired bra made for one sizing study had a centre front gore, cups, cradles, back bands and shoulder straps, with a metal underwire run along the lower edge of each cup through channelling (Peterson and Suh, 2019). The hardware comes as separate accessories: a 2016 chapter in an edited book lists the accessories of intimate apparel as the underwire, hook-and-eye tape, ring and slider, and buckle and bone (Yip, 2016). The table puts each part beside its material and the operation that attaches it in one factory’s breakdown (Atsilia and Isfianadewi, 2025). That study names the machine, not the stitch; the ISO 4915 number in the last column is the one a thread maker’s table for bras gives for that machine’s stitch (Coats, Bras).
| Part | Made of | How it is joined in the study | Stitch (ISO 4915) |
|---|---|---|---|
| Cups | Cut-and-sew: several flat panels of lace or other fabric. Moulded: polyurethane foam or a fabric-foam laminate (one laminate measured 4.25 mm and 287 g/m²; a warp-knitted cup lace, 0.83 mm and 90 g/m²) | Stabiliser attached to the lining at a table; cup and lining joined at the neckline and underarm, catching in the elastic, on zigzag; the moulded cup basted at the underbust on overlock and the underbust stabiliser attached on single-needle; then the cup assembly on zigzag, the longest single operation | Zigzag 304, or 308 for three-step; 504; 301 |
| Cup-to-back seam | The finished cups, centre front and wings | Cups joined to the back assembly on a twin-needle split-bar machine | 301 × 2 (twin-needle lockstitch) |
| Centre front (gore) | Lace assembly on a lining | Lace joined to lining at the bottom on zigzag; joined at the top, turned and the sides basted on single-needle lockstitch | 304 or 308; 301 |
| Wings (back band) | Stretch fabric such as power net, an elasticised warp knit made for foundation garments and bras | Elastic attached at the bottom, the top and the centre back on zigzag, each edge then top-stitched | 304 or 308; 301 |
| Edge and underband elastics | Narrow elastic tape, woven or warp-knitted (crochet elastic) | Zigzag; the thread maker names the 406 twin-needle coverseam for attaching elastic and lace on lingerie | 304 or 308; 406 |
| Underwire | Coated stainless or high-carbon steel, or plastic or resin, with a cover on each tip | Inserted at a hand table, then bartacked (the study lists insert wire and bartack wire) | Bartack (listed as 304) |
| Wire channel | Narrow tape; wire channels are one of the listed uses of narrow elastic tapes | Not itemised: the study lists insert wire loop and trim wire loop at a table without saying what the loop is | Not stated |
| Straps | Narrow elastic tape with a ring and slider | Bartacked to the cup and to the centre back | Bartack (listed as 304) |
| Hook-and-eye tape | Hook-and-eye tape, an accessory | Attached to the wings on zigzag, then a second zigzag operation the study calls sarge hook and eye | 304 or 308 |
Sources for the table: cup materials as measured by Lee (2020); power net as described by Lee (2009); elastic tapes and their uses from Yip (2016); wire materials and tip covers from Lee (2020); the 406 coverseam from Coats, Basic stitch types. The parts are named and drawn on the site’s bra anatomy page, and the styles they make up are on types of bra.
Cut-and-sew cups and moulded cups
A cut-and-sew cup is built from several flat pattern pieces, and where its seams run decides its shape. In a study of prototypes made for one 32D wearer, changing only the seamlines changed the cup volume by up to 13–17% (Peterson and Suh, 2019). Assembling those pieces needs a skilled pattern maker and sewer (Lee, 2020).
A moulded cup has no seams. A flat, flexible sheet of polyurethane foam is pressed between a pair of hot aluminium male and female moulds, at about 200 °C, into the three-dimensional cup shape. Moulding removes the bulky seams and reduces production cost (Wu, Yick, Ng and Sun, 2018). The foam can be laminated to fabric first, and in some designs steel wires and pre-formed components are built into the foam cups during moulding (Lee, 2020). A 2016 chapter in an edited book puts moulded bras at almost 80–90% of the bra market (Yick, Ng and Wu, 2016); its abstract gives no year or basis for the figure, so treat it as an order of magnitude.
| Bra cup moulding | What the paper reports |
|---|---|
| Tooling | In production, a pair of aluminium male and female moulds with matching shapes; the study itself pressed flat foam sheets between two hot, parallel aluminium slabs |
| Mould temperature | About 200 °C in production; the study tested 180 to 210 °C |
| Dwell time | The study tested 60 to 180 seconds, in 30-second steps |
| Foam | Open-cell polyurethane sheet, 10 mm thick; the two foams tested had densities of 28.23 and 45.07 kg/m³ |
| After moulding | The foam shrinks as it cools; moulded cups fit the mould head well only near the cup tip, and cup shape and thickness vary substantially, so the authors call the control of the process still far from reliable |
Source for the table: Wu, Yick, Ng and Sun (2018), Polymers 10(5), 472. Larger cups and fabric-laminated foams need more energy to soften and set (Lee, 2020), so the moulding settings depend on the cup size and the material.
Wired and wireless bras
An underwire is a flat, U-shaped frame under each cup. Metal wires are usually stainless or high-carbon steel with a coating, which also keeps them from rusting; plastic and resin wires are made too. Each end of the wire carries a tip cover so that it cannot work its way out through the bra, and the wire runs in a channel or casing (Lee, 2020). The channel is a narrow tape: wire channels are one of the listed uses of narrow elastic tapes, alongside straps and bands (Yip, 2016).
In the factory study the wire goes in near the end, once the cups are joined to the back: three operations at a hand table (insert wire loop, insert wire, trim wire loop) and then a bartack on the wire. Those four operations take 1.99 of the bra’s standard minutes (Atsilia and Isfianadewi, 2025). A wireless style has no wire, so those four operations are not needed.
The bra manufacturing process, step by step
- Design and pattern. The style is drawn as flat pattern pieces for the cups, cradle, centre gore, wings and straps. Cup seam placement sets the cup’s volume, so new cup patterns are tried as prototypes; in one study they were fitted on the wearer (Peterson and Suh, 2019). The general method is on the site’s pattern making and grading page.
- Size and grade. Each size is a band and a cup, so the pattern is graded across both, band by band and cup by cup (see sizes and standards).
- Cut. Lace, net, lining and laminate are spread, marked and cut to the graded patterns, as in the cutting room of any garment production process.
- Mould (moulded styles only). Foam or laminate is pressed between hot aluminium moulds and left to cool, and the moulded cups are checked before sewing (moulded cups).
- Sew the sub-assemblies. The centre panel, the two back wings with their elastics and hook-and-eye tape, and the cups are made up separately (the sewing line).
- Assemble. The cups are joined to the back assembly on a twin-needle machine, the wires inserted and bartacked, and the straps bartacked to the cup and the centre back.
- Check and test. Cups, elastics and trims are checked against the style’s specification (quality checks).
Sewing a bra: operations, machines and stitch types
A 2025 study of an Indonesian intimate-apparel factory printed the operation breakdown for one wired, moulded style: 22 operations, each with its machine and its standard minute value (SMV: the standard time for an operator to complete the operation by the most efficient method under standardised working conditions). Grouped by sub-assembly, they are:
| Sub-assembly | Operations | Machines | Standard minutes |
|---|---|---|---|
| Centre panel | Join the lace assembly to the lining at the bottom; join at the top, turn and baste the sides | Zigzag; single-needle lockstitch | 0.81 |
| Back wings | Attach elastic at the bottom, the top and the centre back, top-stitching each; attach and finish the hook-and-eye tape | Zigzag; single-needle lockstitch | 2.75 |
| Cups | Check the moulding; attach stabiliser to the lining; join cup and lining at the neckline and underarm, catching in the elastic; baste at the underbust; attach underbust stabiliser; assemble the cup | Hand table; zigzag; overlock; single-needle lockstitch | 3.64 |
| Assembly | Join cups to the back assembly; insert the wire loop, insert the wire, trim the loop; bartack the wire; bartack the straps to the cup and centre back | Twin-needle split-bar; hand table; bartack | 3.20 |
| All 22 operations | 10.41 |
Source: Atsilia and Isfianadewi (2025), Table 1, summed by sub-assembly. The paper gives the bra’s total as 12.03 standard minutes and 602 seconds of process time; the 22 rows it prints add to 10.41 minutes and 565 seconds, and the paper does not explain the difference. Its weekly table of daily targets (1,191 to 1,400 bras) also differs from the 1,047 given with the breakdown. The longest single operation is the cup assembly on zigzag, 58 seconds or 1.162 standard minutes; next come the cup-to-lining join at 0.78 minutes and the two bartacks at 0.758 minutes each.
Stitch types. A thread maker’s recommendations for bras list the stitch types used on them: 301 lockstitch and twin-needle 301, 304 zigzag, 308 three-step zigzag, 504 three-thread overlock and bartack (listed as 304), with needle threads of Tex 24 to 30 and needles of 70 to 90 Nm (Coats, Bras). A zigzag is used where a seam must stretch: a plain 301 lockstitch has low elongation, while the zigzag formation gives the seam more (Coats, Basic stitch types). The same source names the 406 two-needle coverseam for attaching elastic and lace on underwear and lingerie. The numbers come from ISO 4915:1991, Textiles — Stitch types — Classification and terminology; ASTM D6193, Standard Practice for Stitches and Seams, covers stitches and seams for sewn items. The site’s machine stitch classes section describes each class and the thread it uses.
Worked example: how many operators a bra line needs
The inputs come from the same factory study: 12.03 standard minutes per bra, a stated target of 1,047 bras a day, and the longest operation, cup assembly, at 1.162 minutes. The working day is 420 minutes: the weekday hours the paper reports for the author’s internship placement at the factory, 08.00 to 16.00, which it counts as seven hours. The paper does not say its target was set on that day length, so the working below is this page’s own.
| Question | Working | Result |
|---|---|---|
| Operators needed for the target at 100% efficiency | 12.03 × 1,047 ÷ 420 | 30.0 |
| Pitch time: work per operator with 30 operators | 12.03 ÷ 30 | 0.40 minutes |
| Bras a day if one operator does the cup assembly | 420 ÷ 1.162 | 361 |
| Balance efficiency with that bottleneck | 0.401 ÷ 1.162 | 34.5% |
| Operators the cup assembly needs | 1.162 ÷ 0.401 | 2.9, so three |
A line runs at the pace of its slowest station. With one person on cup assembly the line could make only 361 bras a day, about a third of its target, however well the other 29 work. The cup assembly needs three operators, and the cup-to-lining join and each bartack, at about 1.9 to 1.95 times the pitch, need two each. The 30 operators are a 100% figure, and the study names unplanned absences, operator skills, machine problems and human error as the reasons its targets were missed, so a real line plans for less than 100%. Open the line balancing calculator set to this bra: it shows a pitch time of 0.40 minutes, balance efficiency 34.51%, output at the bottleneck 361.45 bras and 29.99 operators needed. Its line efficiency reads 99.96% only because actual output is set equal to the target. The SAM calculator builds a standard minute value from a time study.
Bra sizes: band, cup and the standards behind them
A bra size has two parts, a band and a cup. The European standard EN 13402-3:2017, Size designation of clothes – Part 3: Size labelling based on body measurements and intervals, defines cup size as the difference between bust girth and underbust girth. Its measurement tables are informative: the values and intervals are given as examples of best practice, and each country or company may combine the body dimensions to suit its own needs (EN 13402-3:2017, preview). Part 1 of the series covers terms, definitions and the body measurement procedure, and Part 2 the primary and secondary dimensions.
The international series is ISO 8559, Size designation of clothes: ISO 8559-1:2017, Anthropometric definitions for body measurement; ISO 8559-2:2025, Primary and secondary dimension indicators, which replaced the 2017 edition; and ISO 8559-3:2018, Methodology for the creation of body measurement tables and intervals (catalogue entry for ISO 8559-2:2025).
None of these is one universal bra size system. In the United States a garment sizing standard is a recommendation, not a requirement, and each company sets its own. The band-and-cup system goes back to a method introduced in 1935 and has changed little since: the band is typically the underbust or chest girth rounded up to an even number of inches, and the cup comes from a girth difference. Some brands take that difference from the underbust and others from the chest above the bust, and the offsets companies add range from 0 to 6 inches (Peterson and Suh, 2019). So the same measurements can translate into different labelled sizes from different makers, and a size means what the maker’s own chart says it means. For the factory, every band and cup pair is a separate size to grade, cut and count. For the wearer’s side, see the site’s guide to bra fitting.
Quality checks, common defects and test standards
- Moulded cups. Polyurethane foam shrinks after moulding and cooling, and moulded cups depart substantially from the mould’s shape and thickness (Wu et al., 2018). The factory study checks the moulding at a hand table before the cups are sewn.
- Foam and comfort. Polyurethane foam wicks moisture poorly and changes colour easily. Spacer fabrics need no lamination and exchange moisture better, and punctured (perforated) urethane sponge breathes better than solid sponge but costs more and holds its shape less well (Lee, 2020).
- Wire poke-through. Each end of an underwire carries a tip cover so that the wire cannot work its way out through the bra (Lee, 2020). The underwire channel calculator compares the force at a wire tip with the channel’s puncture resistance.
- Elastics. ASTM D4964, Standard Test Method for Tension and Elongation of Elastic Fabrics, covers wide or narrow elastic fabrics on a constant-rate-of-extension tester, at loop tensions or elongations agreed between the parties (ASTM catalogue). Lee (2020) used it to test the elastic tapes for straps and bands. The elastic stretch and recovery calculator turns a stretch test into elongation, recovery and set.
- Fabrics. ISO 20932-1:2018, Determination of the elasticity of fabrics, Part 1: Strip tests, measures elasticity on strips or loops of fabric, but excludes narrow fabrics (catalogue entry); the narrow elastics are covered by ASTM D4964 above.
- Trims. Trims such as hooks and eyes and sliders go through physical strength and performance tests, for example pull-off and slippage resistance and slider deflection and recovery after pull, run to ASTM, ISO, EN and other national standards or to the manufacturer’s or client’s own specification (Hong Kong Qualifications Framework, unit 105863L4).
- The line. In the factory study, production targets were missed through unplanned absences, operator skills, machine problems and human error.
Questions
How are bras made?
In a factory the pattern is graded into band and cup sizes and cut, the cups are sewn from panels or moulded from foam at about 200 °C, and the centre front, wings and cups are sewn on zigzag, lockstitch and bartack machines. The wires go into their channels at a hand table and are bartacked in, then the hook-and-eye tape and straps are attached and the bra is checked.
What is the bra manufacturing process?
Design and pattern, size grading, cutting, cup moulding for moulded styles, sewing the centre panel, wings and cups, assembly with wires and straps, then checks and tests. One factory study itemises 22 sewing and handling operations for a wired, moulded bra.
What machines are used in bra manufacturing?
Zigzag lockstitch machines (304, and 308 for three-step) for elastics, cups and hooks and eyes; single-needle and twin-needle lockstitch (301) for top-stitching and joining; overlock (504); bartack machines for the wire channels and straps; and, for moulded cups, a press with heated aluminium male and female moulds.
How are moulded bra cups made?
A flat sheet of polyurethane foam, alone or laminated to fabric, is pressed between hot aluminium male and female moulds at about 200 °C and held for a set dwell time; one study tested 60 to 180 seconds on flat foam sheets. The foam shrinks as it cools, so cups are checked before sewing.
What materials make a bra breathable and comfortable?
Polyurethane foam cups wick moisture poorly, so spacer fabrics, which need no lamination and exchange moisture better, and punctured urethane sponge are the more breathable alternatives. Stretch in the wings and elastics also matters, which is why elastic tapes are chosen on elongation, modulus, durability and handfeel.
How long does it take to sew a bra?
It depends on the style. A 2025 factory study gives 12.03 standard minutes for one wired, moulded bra, with the cup assembly the longest single operation at 1.162 minutes. At that content, 30 operators working at 100% efficiency for 420 minutes (7 hours) make about 1,047 bras.
Sources
- Operation breakdown, standard minutes, working day and causes of missed targets: S. A. Atsilia and D. Isfianadewi, “Implementation of Standard Minute Value (SMV) to Achieve Bra Production Target […]”, an internship research report on an Indonesian intimate-apparel factory, Jurnal Indonesia Sosial Teknologi 6(1) (2025), 590–606, doi:10.59141/jist.v6i1.1352.
- Cup moulding: L. Wu, K. L. Yick, S. P. Ng and Y. Sun, “Modeling of flexible polyurethane foam shrinkage for bra cup moulding process control”, Polymers 10(5) (2018), 472, open access; K. L. Yick, S. P. Ng and L. Wu, “Innovations in the bra cup molding processes”, in Advances in Women’s Intimate Apparel Technology (Elsevier, 2016), 69–87, abstract.
- Parts, cup seams and sizing practice: A. Peterson and M. Suh, “Exploratory study on breast volume and bra cup design”, Journal of Textile and Apparel, Technology and Management 11(1) (2019), open access.
- Moulded bra components, underwires, cup materials and the elastic test: C. W. Lee, Ergonomic design of supportive moulded bras, MPhil thesis, The Hong Kong Polytechnic University (2020), full text.
- Accessories and elastic tapes: Y. W. Yip, “Innovative accessories for intimate apparel” and “Narrow fabric elastic tapes”, in Advances in Women’s Intimate Apparel Technology (Elsevier, 2016), abstract and abstract.
- Power net: C. G. Lee, “Treatments of ceramic powers, capsules, and plasma in the power net warp knitting fabric”, International Conference on Dyeing and Finishing, Daegu (2009), paper.
- Stitch types and threads for bras: Coats, Bras and Basic stitch types.
- Standards, from catalogue entries of standards bodies and publishers: EN 13402-3:2017 (SIST preview); ISO 8559-1, -2 and -3, ISO 4915 and ISO 20932-1 (Estonian Centre for Standardisation and Accreditation catalogue); ASTM D4964 and D6193; trim tests from the Hong Kong Qualifications Framework unit 105863L4.
How this page is kept
Last verified 12 October 2026. Every figure on the page was read in the source named beside it on 11 or 12 October 2026: process figures from the factory study and the moulding paper, materials from the book chapters and the thesis, stitch types from the thread maker, and standard titles from the publishers’ catalogues. The worked example uses the site’s line balancing calculator as it stood on 12 October 2026. Figures that describe one factory or one study are labelled as such and are not industry averages.
Change log. 12 October 2026: rewritten in full, and the 2012 page on bra manufacturing reviewed for anything worth carrying. Removed from the earlier version of this page: repeated sections on careers, ERP, blockchain, digital twins and future trends; six case studies of unnamed companies, two of them with round percentages, none with a source; the statement that bras must meet FDA standards; and the claim that the first modern bras of the early 20th century had underwires and padded cups, for which no source was found. Not carried from the 2012 page: its statement that spandex is processed from Malaysian tree sap, because spandex is a manufactured fibre of at least 85% segmented polyurethane (16 CFR 303.7), and its tolerance figures for finished bras, which could not be traced to a source.
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