How to Start a Swimwear Line: The Numbers Nobody Else Will Publish

Every “how to start a swimwear line” guide you’ll find this week was written by one of two people: a print-on-demand platform trying to move you onto their dropship plan, or a factory that will happily explain the seven steps to launching a brand — and then ask you to “contact us for a quote” the moment you get to fabric, MOQ, or price. We checked. Printful’s guide gives you a MOQ range and a market-size stat, then routes you to sign up for free. A swimwear factory’s own guide gives you a 100–500-unit MOQ range, a 4–6 week lead time, and not one dollar figure. A sourcing agency’s guide has twelve steps and a 90-day roadmap and doesn’t mention a single number you could plan a budget around.

We’re a factory in Suzhou, Jiangsu. We manufacture bikinis, one-pieces, tankinis, and rash guards. Below is what those guides leave out — because we publish it on our own site anyway, and there’s no reason to hide it from you here.

A print-on-demand platform’s business model depends on you never building factory relationships — every step in their guide leads back to “start for free” on their own tool. A factory’s marketing blog has the opposite incentive: give you just enough to sound credible, then convert the real numbers into a sales call, because a live conversation is where a vague “100–500 units” becomes whatever price closes the deal that week. A sourcing agency’s guide is written to sound comprehensive without being falsifiable — twelve steps you can’t fact-check against anything.

None of that is dishonest, exactly. It’s just incomplete in a way that costs you time. So here’s the version with the numbers left in.

Before you read another word about fabric weights or MOQs — if you’re testing a design concept, don’t have $1,500–3,000 to commit to a first production run, or you’re not sure swimwear is even your category yet, print-on-demand is the right call, not bulk manufacturing. POD gets you a live product page in days with zero inventory risk. It also caps your margin at roughly half of what bulk production delivers, and drop-ship swimwear fabric quality is generally a step below what a dedicated swim-fabric mill produces.

Bulk OEM production makes sense once you’ve validated that people will actually buy — a capsule of 2–6 styles that sold through a soft launch, a waitlist with real deposits, or an existing audience you’re converting into a product line. If that’s where you are, the rest of this applies to you.

Every guide mentions a tech pack. Almost none show you why swimwear’s tech pack is different from a t-shirt’s. Swimwear fit is unforgiving — a 2mm error in an elastic casing measurement shows up as a visible pucker on stretched fabric, in a way that never shows on a woven shirt. Your tech pack needs, at minimum: flat sketches front and back, a graded size spec sheet, lining construction notes (full lining vs. gusset-only), seam type per panel (flatlock vs. overlock vs. bound), elastic width and stretch percentage at leg openings and waistband, and a hardware spec if there’s underwire or adjustable straps.

We wrote a full walkthrough of what a tech pack needs to contain and why factories reject incomplete ones — read the clothing tech pack guide before your first supplier call, not after your first rejected quote request.

“Premium stretch fabric” tells you nothing. Here’s what we actually run and why it matters:

Spec	What we use	Why it matters
Composition	82% nylon / 18% spandex, or 80% polyester / 20% spandex	Nylon blends hold shape and color better against chlorine and sun; polyester blends cost less and resist chlorine degradation slightly better for pool-heavy use cases
Weight	190–220 GSM	Below ~180 GSM, fabric goes sheer when wet — the single most common first-order complaint from new brands who chose fabric on look alone
Construction	Warp-knit tricot, four-way stretch	Four-way stretch (vs. two-way) is what lets a suit recover its shape after sitting wet against skin for hours

If a supplier can’t give you a GSM number and a stretch-direction spec on request, they’re quoting fabric they haven’t actually tested for swim use. Ours is certified under OEKO-TEX Standard 100 (certificate SH025 206558, tested by TESTEX Zurich) and, for recycled-content orders, Global Recycled Standard (certificate 4.0 TE-00110085, Intertek). Ask any manufacturer for their certificate numbers directly — a real certification always has one, and it’s independently searchable.

This is the step where vague guides cost you the most money. “MOQ: 100–500 units per style” sounds like a range you can plan around. It isn’t a real number until you know whether it’s counted per style or per colorway, and whether sizes have to be pre-allocated or can flex.

Most overseas factories quote 500–1,000 pieces per style before they’ll even sample it. Ours is 100 pieces per colorway, with sizes mixed freely. Custom woven or printed labels have their own minimum, 200 pieces per colorway, separate from the garment MOQ. That distinction — per colorway, sizes flexible — is worth asking every manufacturer you talk to, because “per style” MOQ from a factory running 5 colorways means you’re actually committing to 500+ units on your first order, not the 100–500 the guide implied.

If your budget genuinely can’t support garment MOQ yet, that’s a real constraint worth planning around before you approach factories — see our breakdown of how low-MOQ manufacturing actually works across categories, including which corners get cut to hit very small runs.

This is the table every guide we checked skipped entirely. FOB pricing, published, not quoted after a call:

Category	Small batch (100–299 pcs)	Bulk (1,000+ pcs)
Bikini / two-piece	$3.00–4.50 FOB	$1.85–2.75 FOB
One-piece	$4.00–5.50 FOB	$2.50–3.50 FOB
Rash guard / cover-up	$2.50–3.80 FOB	$1.60–2.30 FOB

FOB means the price at the China port (Shanghai or Ningbo) before your freight and duties — budget separately for that, or ask for DDP (door-to-door, duty paid) pricing if you’d rather have one landed number. Payment is typically 30% deposit to start production, 70% before the goods ship. Run your own numbers against these tiers before you talk to anyone — it’s already published, no quote request needed to see it.

1. Sampling: 7–10 workdays.
2. Bulk production: 18–25 days after sample approval, for a standard first order.
3. Reorders: 10–15 days, once a tech pack and approved sample already exist on file.
4. Quote turnaround: 8–12 hours for an itemized quote once you send specs — if a supplier takes days to answer a spec question, that’s a preview of how production communication will go.

Compare that to “4–6 weeks” or a 90-day roadmap with no day-level breakdown — vague timelines are usually vague because nobody’s tracking them against a real production floor.

Swimwear fails in specific, predictable ways: chlorine-faded color after repeated wash cycles, lining separating from shell fabric at the seam, elastic losing recovery after stretching. Ask what quality standard your factory inspects against before shipment — AQL 2.5 is the acceptable-quality-limit standard we run pre-shipment inspection against, meaning a defined maximum defect rate per batch size before a shipment is rejected or reworked. If a factory can’t name their AQL standard, they don’t have a formal inspection process — they’re checking “does it look okay.” If a batch fails AQL 2.5 on pre-shipment inspection, it does not ship — it gets reworked or remade before it leaves the factory, not after it lands on your dock.

Ask any manufacturer for three things before you commit: their business licence, their certification numbers (OEKO-TEX/GRS — checkable in the issuers’ public databases in about two minutes), and a proto sample sewn on their own production line. A trading company can forward photos of someone else’s factory floor, but it cannot sew your proto sample in-house in 7–10 workdays. We also work on 30/70 terms or full Alibaba Trade Assurance escrow, so your deposit stays protected until the goods exist and pass inspection.

• Choosing fabric by photo, not GSM.
• Ordering pre-allocated sizes instead of a mixed-size MOQ. Committing to fixed size breakdowns before you have any sell-through data means you’re guessing twice — once on style, once on size curve.
• Skipping a wear-test sample round. A sample that looks right on a mannequin can still fail on a body in motion — one additional wear-test round before bulk catches most seam and elastic issues.
• Not asking how bulk deviation from sample gets handled. Get this in writing before you pay a deposit, not after bulk arrives different from what you approved.