TL;DR
Agree one measurement sheet with stated tape positions, grade plus size styles on their own block, then confirm stretch, closures and fit photos before approving a size run.
Measure the wearer, not the letter size
Letter sizes carry very little information on their own. A medium from one supplier can sit closer to a large from another, and costume patterns often include less ease than everyday clothing because the look depends on a shaped silhouette. Before you compare quotes, agree on a measurement set: bust or chest, waist, hips, inseam, shoulder width, sleeve length, back length and wearer height.
Ask each supplier to state where the tape is placed on the garment. A waist measured at the natural waist and the same waist measured at a dropped waist give different numbers, and a size chart without tape positions invites two readings of one line. Keep a single measurement sheet for the whole range and use it for every style, so fitting comments from a sample become a written change rather than a new discussion at production.
Why plus size lines need their own grade
Plus size Halloween costumes are not a scaled-up version of a straight-size pattern. Scaling by a fixed ratio distorts proportions: armholes deepen, shoulders widen and the balance between waist and hip shifts. A plus size grade usually needs separate pattern work, more fitting points and a different placement for darts, closures and trims.
Treat plus size costumes as their own block. Confirm the size run, the grade increment between sizes, and whether the style is fitted on real bodies in at least the smallest and the largest size of that run. If one pattern is offered across the whole run, ask how it was graded and look closely at the fit photos for the largest size, where proportion problems appear first.
Fabric and closures decide comfort
A costume is worn once or twice, but the wearer still has to move, sit and reach. Stretch knits forgive small grading errors; woven fabrics without elastane expose them. Ask for fabric composition, stretch direction, stretch recovery, and whether the garment is lined where it touches skin.
Closures decide whether the style is worn at all. A back zip that cannot be reached without help, a hook that opens when an arm is raised, or a bodice with no adjustment will produce returns. Try the sample on a real person in the target size and note every point where the wearer needed assistance.
Women's, men's and unisex blocks differ
Womens Halloween costumes are usually drafted with bust shaping and a closer waist, while mens Halloween costumes rely on shoulder and chest ease with a straighter line. Unisex sizing is often a men's block with a shorter run, which fits some wearers poorly. Decide which block each style uses and state it in the product data, so someone ordering Halloween outfits online knows what to expect.
Where a range covers both groups, publish two size charts instead of one merged chart, and mark the styles that can be worn by either. Keep the naming consistent across listing, carton label and packing list, because a mismatch between those three documents is a common source of picking errors.
Review checklist before you approve a size set
Use the same checklist for every style so that decisions stay comparable across factories and seasons.
- Measurement sheet with tape positions for every point
- Grade increment stated per size, not per run
- Fit photos in the smallest and largest size of the run
- Fabric composition, stretch direction and recovery
- Closure type and every adjustment point
- Lining or skin contact notes
- Garment length compared with wearer height
- Care instruction available from the fabric supplier
What to request with the sample
Ask for one sample per size group rather than one average size. Measure each sample yourself, write the numbers down, and keep the record with the order. If a later shipment differs, that record is the reference point for the conversation.
No checklist guarantees a fit, but it turns a vague complaint into a measurable line item that a factory can correct.