Pattern reduction is the difference between a target body dimension and the corresponding relaxed garment dimension. It helps a close-fitting garment engage the body, but a single reduction percentage across every panel and size cannot account for material direction, body proportions and construction.
Use the right denominator in development calculations
If body circumference is B and relaxed garment circumference is G, reduction relative to the body is (B minus G) divided by B. Required garment extension is (B minus G) divided by G. The two percentages differ because they describe different starting points.
Hypothetical example: for a 100 cm body and an 85 cm relaxed garment, reduction is 15%, while required extension is about 17.6%. This is arithmetic illustration, not a recommended pattern reduction. It gives no pressure value and cannot replace fitting or material characterization.
Break the garment into functional regions
List chest, waist, hip, upper arm, thigh or other relevant regions separately. Consider vertical length as well as circumference. Reducing a torso circumference does not establish the correct sleeve length, armhole shape or rise. A garment may be tight in one location while still migrating because another region is poorly balanced.
Map material direction and seam position onto the pattern. The same knit can offer different resistance along its length and width. Mesh, double layers, elastic bands and decoration can change local extension. Review these transitions rather than treating the garment as a uniform tube.
Test the grade against actual body ranges
Start from the target body distribution and the product’s intended fit. Check the lower and upper ends of each proposed size range and relevant body proportions. An equal increment between sizes may be a convenient starting point, but it needs evidence where chest, waist, hip or limb proportions change differently.
Do not assume that larger sizes necessarily need the same reduction or that they automatically provide less compression. Compare the actual relationship among body measurements, garment dimensions and material behavior. Where a pressure profile is specified, confirm it on the relevant finished samples using the agreed measurement method.
Change one cause at a time during correction
When a sample binds at the armhole, investigate local shape, sleeve balance, fabric direction and seam extension before enlarging the entire top. When a hem rides up, examine torso length and movement pull as well as hem circumference. A broad adjustment may hide the original issue while creating looseness elsewhere.
Keep the pattern revision, material and construction constant when testing a particular correction where practical. If several inputs change together, record them and avoid attributing the improvement to one factor without evidence. Save failed samples or clear photographs when they explain why the pattern was revised.
Multi-size reduction and risk record
Use this record for each region and size rather than one percentage on the cover of the tech pack. It connects the calculation to the actual approval evidence.
| Record element | Entry | Risk to review |
|---|---|---|
| Body region and size | [Chest / waist / limb region and size] | A single circumference may hide local fit issues |
| Target body range | [Lower, middle and upper measurements] | Boundary wearers may differ from the base fit |
| Relaxed garment | [Measurement and pattern revision] | Production variation changes intended extension |
| Calculated relationship | [Reduction and extension, with denominators] | Percentages may be mistaken for each other |
| Material direction | [Fabric reference and panel orientation] | Directional resistance may differ |
| Observed behavior | [Restriction, migration, opacity, seam response] | Calculation alone cannot approve wearing fit |
| Measured claim if applicable | [Finished-garment report and conditions] | Fabric data cannot establish local pressure |
| Correction and retest | [Change, owner and affected sizes] | One-size correction may disrupt the grade |
Release a validated size set, not just a formula
Review the size-set evidence before cutting production. Confirm that each approved region has a defined measurement method and tolerance, and that the material used for validation is the production reference. Repeat affected checks after care where dimensional or recovery changes could alter the fit.
The final technical pack can include the development calculations, but the manufacturing standard should identify the approved pattern, measurements and construction. Pattern reduction supports a sportswear fit decision. It is not a shortcut to prescribing medical compression or proving a recovery benefit.
Related purchasing guidance
Continue with How should we size a compression top: by garment measurements or by the body it should fit?, or How do we decide the size range and negative ease for our leggings so each size fits across the range?.
