Undershirt Manufacturing

Undershirts are judged on three things the customer never sees written down: neckline depth, body length, opacity.

The most specification-sensitive garment in a basics range: how deep the V sits under a collar, how long the body runs against a tuck, and how white the shirt stays after ten washes.

Three routes cover all 35 articles in this cluster
Four specifications decide whether a pack is repurchased
Every route ends in a measurement you can put in a tech pack

Start an undershirt programme

Crew neck cotton undershirts manufactured for basics brands

Three routes, and you only need one of them

Start from the neckline, from the fabric, or from the pack the customer buys.

Neckline depth is the whole point of an undershirt

Two factories can both make a deep V and produce garments that sit an inch apart. Measure the front depth from the shoulder seam and the width across the collar opening, and put a wash-test result against both, because a V that starts correct can still open up after five washes. This is the specification undershirt buyers leave out most often and then blame the factory for. Write it down as a number and the argume…

White opacity is a specification, not a preference

A white undershirt that shows the body under it is a return, and returns on multipacks are the most expensive kind because the customer sends the whole pack back. Opacity depends on the yarn count, the fabric weight and the knitting structure, and it degrades with washing. Ask the factory for a light-box check and a wash test on the actual fabric rather than approving a swatch, and treat the result as part of the …

Weight follows the season and the layering

Summer programmes want a light, breathable jersey that stays opaque; winter programmes want a heavier fabric, often with a brushed inner face or a rib structure. Buying one weight and running it year-round is the cheapest way to be mediocre in both seasons. Plan the weight band per season and keep the neckline and body block constant, so the fit story stays consistent as the range expands.

What goes wrong in bulk

Neck rib recovery, side seam twisting, shade variation and size drift account for almost every complaint.

Body length is a tuck decision

Specify the body length from the high point of the shoulder and check it against the torso the garment is replacing, then check the hem width against the hip. Buyers routinely fix a tuck problem by adding a size, which changes the neckline and the armhole at the same time. Measure the sample flat and compare the numbers with the garment the customer already wears, because that is a better reference than any size chart.

Private label undershirts live or die on reorders

Undershirts sell in packs to customers who come back, which means the reorder cycle matters more than the launch. Set the reorder trigger as a percentage of the first order sold, keep the cash for the repeat, and specify that the repeat runs against the same sealed reference, the same fabric lot discipline and the same neckline measurements. A pack that arrives with a slightly different white is a pack the customer notices.

What goes wrong in bulk

Inspect at mid-production on a first order and at packing from the second, against the sealed reference. Check the neck rib after a wash, the side seam for twisting, the shade against the approved swatch, and the measured points across the size set. Record defects as counts rather than impressions so the conversation with the factory is about numbers. The defect field guide below lists what to look for, in the order it appears.

Approve the size set, then align the claims

An undershirt has to behave the same across five sizes under a dress shirt.

Approve the size set, then align the claims

An undershirt has to behave the same across five sizes under a dress shirt, which is why the size set matters more here than in any other category. Approve it against measured points and a wash test. Then align the claims — organic, moisture-wicking, anti-odour — with the test reports, because the multipack format means a failed claim is a failed pack rather than a failed single unit.

Labels, packaging and the pack decision

Decide the pack format before the packaging: a two-pack, three-pack or single, with or without a belly band, in a polybag or a printed box. The pack drives the barcode placement, the suffocation warning and the FBA prep, and each of those is cheaper to specify at sampling than to retrofit at packing. Keep the label wording compliant for every market the pack will ship into.

Four specifications decide an undershirt

Everything else on this page follows from these four.

Neckline depth from the shoulder

Two factories can both make a deep V and produce garments that sit an inch apart. Measure it, then wash it.

Opacity tested, not assumed

Yarn count, GSM and knit structure decide whether a white shirt shows the body under it.

Body length against the tuck

An undershirt that comes untucked is a length problem, not a size problem.

Weight by season

A 150 GSM summer shirt and a 220 GSM thermal are different products, not different colourways.

Where to go from here

The guides around undershirt programmes.

T-Shirt Fit and FabricThe knit specifications undershirts share.

Men’s Underwear ManufacturingThe adjacent basics programme.

Apparel Fabric SelectionFibre and weight selection.

Clothing Factory SourcingLabels, packs and shipping.

Undershirt questions

What fabric weight should an undershirt be?

Roughly 140 to 170 GSM for a summer undershirt that stays opaque, and 200 to 240 GSM for a winter or thermal programme. Below about 140 GSM the white versions begin to show through.

How deep should a V-neck undershirt be?

Deep enough to stay hidden under an open collar, which in practice is 15 to 18 cm from the shoulder seam on a men’s medium, verified on a washed sample rather than a new one.

Should undershirts be combed cotton?

For a basics line, yes. Combed cotton pills less and holds its surface, which matters more on an undershirt than on a t-shirt because it is washed more often.

How many sizes should a multipack range cover?

Five or six. Undershirts sell in packs, so a missing size means a missing pack, and the top two sizes are usually the ones that run out first.

What causes side seam twisting?

Usually insufficient fabric relaxation before cutting, or a tubular knit cut off-grain. It is a process problem at the factory, and it shows up after one wash on a sample.

Start an undershirt programme

Send the neckline, the weight band, the pack format and the destination market, and we will come back with a construction, a size set and an opacity test on the fabric.

Send your undershirt spec