Production Tolerance Standards for Stretch Garments

Tolerance arguments start with a tech pack that says plus or minus 5 millimetres on every measurement. That looks rigorous and is unusable: 5 millimetres on a 300 millimetre underband is 1.7 percent, which is achievable, while 5 millimetres on a 20 millimetre strap width is 25 percent, which is not a tolerance at all. Stretch garments need a different approach because the material itself moves, and the tolerance has to move with it.

Why Stretch Tolerances Are Different

A woven garment is measured in a stable state. A knit with elastane is not: the same bra measures differently depending on how long it has been lying flat, how it was handled, and how the operator holds the tape. Before you can enforce a tolerance you have to define the measurement condition, not just the value.

State the condition for every measurement. Underband relaxed means laid flat without tension after a defined relaxation period. Underband stretched means extended to a defined force or to a defined percentage, measured on a gauge rather than by hand. Without that, two inspectors will produce two different numbers from the same garment.

Percentage Versus Millimetre

Use percentage tolerances for dimensions that scale with the garment, and millimetre tolerances for fixed components. This keeps the tolerance meaningful across the size range instead of tight at one end and loose at the other.

A workable starting table for a medium impact bra: underband relaxed length plus or minus 2 percent; underband stretched length plus or minus 3 percent; cup width and depth plus or minus 3 millimetres; wing height plus or minus 3 millimetres; strap length from the convergence point plus or minus 5 millimetres; cut-out position plus or minus 3 millimetres; hook overlap plus or minus 2 millimetres; strap and band elastic width plus or minus 1 millimetre; pad pocket opening plus or minus 3 millimetres.

Fabric Tolerances

Tolerance starts at the roll. Common acceptance: GSM plus or minus 5 percent, usable width plus or minus 1 centimetre, stretch percentage plus or minus 5 percent of the specified value, and recovery not less than the agreed minimum, typically 90 percent. Agree whether width tolerance applies to usable width after removing the selvedge, because that is the number that affects the marker.

Require dimensional change testing to AATCC 135 or the ISO 6330 equivalent, with an agreed maximum, and record it per dye lot rather than once per fabric.

Component Tolerances

Elastic and hardware have their own tolerances and they are usually looser than buyers assume. Elastic width of plus or minus 1 millimetre is reasonable; expecting plus or minus 0.5 millimetres on a knitted elastic will be priced as a premium item. Hook tape position relative to the band edge should be held tighter, at plus or minus 2 millimetres, because a misaligned hook row is visible and functional.

Writing It Into the Tech Pack

Put the tolerance next to each measurement in the graded spec table, not in a general note. Add the measurement condition. Add the inspection method: how many pieces per size, whether the inspector records actual values or pass or fail, and what happens on a borderline result.

Enforcement

Tolerances only matter if they are applied. Instruct inspection to measure at least 10 pieces per size spread across production dates and to record actual values. A run where every piece sits at the top of tolerance is passing and drifting at the same time, and the value record is what lets you intervene before the next order.

Keep a sealed reference sample per size. When a dispute arises, the reference and the written tolerance resolve it quickly; without both, it becomes a negotiation.