An undershirt shrinkage specification should protect the dimensions the wearer needs after care: enough body length for the intended wearing position, acceptable chest ease and stable neck and arm openings. A single “maximum shrinkage” percentage can miss a garment that becomes shorter but wider, or a neckline that changes while the body passes.
Begin with the washed fit envelope
Approve a washed garment on the target wearer group before assigning commercial limits. For each critical point, define an acceptable finished dimension range after the stated care conditions. Keep that range separate from the percentage change limit and the manufacturing tolerance on the new garment.
A garment can have a small percentage change yet end up too short if it started near the lower new-length tolerance. Conversely, a garment deliberately cut with allowance can meet the washed fit even when its percentage change is larger. Decide which dimensional-change and finished-fit conditions must both pass; do not allow one to cancel the other silently.
Use separate point-of-measure records
| Point | Before care | After care | Use requirement |
|---|---|---|---|
| Front/back body length | Named shoulder datum to finished hem | Same datum and direction | Approved tucked or untucked coverage |
| Chest and hem width | Flat width at defined positions | Same positions without stretching | Ease without excess tension or bunching |
| Neck width/front drop | Finished opening endpoints | Same endpoints and relaxation | Coverage and neckline position |
| Sleeve/armhole | Length, opening or depth as applicable | Matched point-of-measure method | Movement and skin comfort |
| Twist or distortion | Seam alignment and reference photo | Recorded alignment change | Seams remain in acceptable positions |
Record actual numbers by sample and size, not only “pass.” Averages can conceal one garment or direction outside the limit. Define how individual results and any summary values are used in the acceptance decision.
Fix care and measurement conditions
State the method, edition, wash and drying choices, cycle checkpoints, specimen state and conditioning or relaxation before measurement. Have the laboratory confirm whether it is testing fabric specimens or finished garments and choose the suitable procedure. Use care conditions consistent with the label.
The existing guide to writing a reproducible shrinkage test covers the general method choices. This undershirt record adds the finished fit constraints. Do not assume a fabric report alone establishes the effect of seams, neckbands, garment finishing and pattern allowances.
Calculate signed change and check the remaining size
Signed dimensional change is (after-care dimension minus before-care dimension) divided by the before-care dimension, multiplied by 100. Under this convention a negative value indicates shrinkage and a positive value growth. Write the convention on the sheet so a positive figure is not mistaken for shrinkage.
Hypothetical example: a body length changes from 72 cm to 69 cm. The change is approximately −4.2%. If the hypothetical buyer’s approved washed minimum is 70 cm, this sample fails the finished-length requirement even if a separate illustrative shrinkage cap were 5%. These are teaching values, not recommended dimensions or universal limits.
Repeat the calculation independently for width and other points where percentage change is relevant. Then compare the actual post-care dimensions with the fit range for that size. Retest movement where the dimensional change could affect coverage.
Choose the correction from the pattern of failure
If body length decreases while width increases, review fabric relaxation and finishing with the supplier. The shorter-and-wider knit explanation describes that related mechanism. If only the neckline distorts, investigate band/body compatibility and attachment. If one size fails while the rest pass, check the size grade and starting dimensions as well as the material.
Pattern compensation should follow verified material behavior. Adding length to every garment does not solve inconsistent lots, and it may make the new garment too long. Approve any revised sample both before and after care, including the smallest and largest sizes and any problem size.
Release with a repeatable record
Keep the approved new and washed samples, measurement sheet, care programme and acceptance decision together. Carry the same conditions into bulk checks and reorders. State which fabric or finishing changes reopen approval.
Provide this record with the undershirt development specification through Knitwear Base. Ask for proposed achievable tolerances against the actual material rather than accepting a generic shrinkage percentage as the entire fit guarantee.
