Why grading up is not enough
Grading is the process of turning one fitted base size into a full size range using grade rules. It works well across a few sizes on either side of the base. Stretch it too far and proportions drift: the rise ends up too short, the waistband sits in the wrong place, the bra underband and cups no longer relate to each other, and the seat shaping lands where it does not belong.
Bodies do not scale evenly. As sizes increase, the relationship between waist, hip, thigh and rise changes, and that change varies between people. A plus-size range therefore needs its own fitted base size and its own grade rules, checked on real bodies in motion. Treat it as a separate development track, even if it shares fabrics and colors with the straight-size range.
Common problem areas and fixes
| Problem in wear | Usual cause | Development fix |
|---|---|---|
| Waistband rolls down when bending | Back rise too short; band too narrow or soft | Raise back rise; wider multi-layer band; refit seated |
| See-through at seat or thigh | Fabric stretched further on larger sizes | Approve opacity on the largest size and lightest color |
| Seam pulling at crotch | No gusset or gusset too small | Gusset sized per size group, not one size for all |
| Pilling or wear on inner thigh | Friction during movement | Pilling test on finished fabric; consider smoother face |
| Bra band rides up | Underband and cup graded together from a small base | Separate plus-size bra block; firmer underband |
| Top rides up in forward fold | Length graded by width, not torso length | Add length; hem with some weight |
Fit models and fit sessions
Use a fit model in the plus-size range for the base size of that range, and if possible a second tester at the top of the range. Fit sessions should include the poses customers actually practice: forward fold, down dog, wide squat, seated cross-legged, lunge and lying on the back. Record comments by pose. "Back waistband slides down in down dog" is far more useful to a pattern maker than "waist feels loose".
Plan for more than one fit round. A first sample often fixes the big issues, and a second sample refines the waistband and gusset. First samples typically take 7-15 days, so a second round adds a few weeks to the calendar. That time is better spent before bulk than after returns. The sampling process note explains how to run rounds efficiently.
Grade rules and the size chart
Write grade rules for each measurement point and each size step, and do not assume the steps are equal across the whole range. Many brands use larger steps in the plus-size range for waist and hip, with smaller adjustments in rise and length. The partner factory's pattern room can propose rules, but the brand should approve them against its own customer data.
Publish a size chart that reflects body measurements, not garment measurements, and explain how to measure. Clear sizing reduces exchanges more than any fabric choice. Our size chart and grading note walks through grade rule tables.
Fabric: opacity, stretch and friction
A larger garment is not stretched the same amount as a smaller one on its intended wearer; depending on the fit, fabric on the seat and thighs can be under more tension. That makes opacity the first fabric decision. Fitted leggings typically sit at 230-280 GSM. Dark colors may be opaque at 230-240 GSM, while white and pastels often need 280-300 GSM. For plus-size lines, run the squat check on the largest size in the lightest color, because that is where opacity fails first. See the squat-proof test note.
Spandex share affects both comfort and hold. Around 15% feels like comfortable stretch, 20-25% is common for supportive leggings, and 25% or more feels compressive. Offer the hold customers ask for, and avoid describing it in shaping terms. Stretch and recovery to ASTM D2594 tells you whether the fabric returns to shape at knees and seat after a class.
Inner-thigh friction is a frequent complaint. Pilling resistance to ASTM D4970 or ISO 12945-2 on the finished fabric is worth requesting, and a smoother, unbrushed face can hold up better in that area. The pilling resistance note explains the test.
Construction details
- Gusset. A diamond or triangle gusset reduces stress at the crotch seam in wide stances. Size it per size group; see gusset design.
- Waistband. A wide, multi-layer band with a raised back rise holds position better than a narrow elastic. Band height is confirmed on the tech pack.
- Seams. Flatlock or coverstitch seams lie flat and reduce chafing. Seam placement on the inner leg should avoid the highest-friction zone where possible.
- Bras. Plus-size bras usually need their own block, with a firmer underband, wider straps and cups sized for the range. Removable cups add flexibility.
- Tops. Add torso length, not only width, and choose a hem that stays down in inversions.
Seamless or cut and sew
Seamless garments are knitted as tubes on circular machines, and the size range depends on the machine and knit program. Some seamless styles cover a broad range of bodies through stretch, but fit control at the top of a plus-size range is often easier in cut and sew, where pattern pieces can be shaped size by size. Cut and sew also allows gussets, pockets and removable pads. Typical reference MOQs are 100-300 pieces per style per color for cut and sew and 300-500 for seamless, confirmed in writing for each program.
Ordering the size curve
Sizes can usually be mixed within the MOQ, which lets a first order follow a cautious size curve. Use sales data from any existing range, and keep a record of which sizes sell through first. Bulk production is typically 30-45 days after sample approval and fabric availability, so reorders on the fastest sizes need to be planned early.
Words and imagery
Describe the garments by fit and function: high-rise, opaque, soft, supportive, pocketed. Avoid shaping and medical language. Show the clothes on people who reflect the size range, in real poses. Customers judge a plus-size line by whether it was clearly made for them.
The plus-size yoga wear hub has garment starting points. When you have a size range, base size and target styles, send the brief to the desk.