Size Curve Planning

Every brand’s customers are different. A streetwear brand with an oversized fit sells a different curve from a fitted activewear brand, and a surf brand’s boardshorts sell differently from its tees. Build the curve from what your customers actually keep.

1. Pick a comparable style or category from the last season or two.
2. Pull units sold by size. If a size sold out early, note the date. Sales stopped because stock ran out, not because demand did.
3. Subtract returns by size. A size with high fit returns is selling more than it should, because some of those customers wanted a different size.
4. Turn the net units into proportions. That is your starting curve.
5. Adjust for sold-out sizes: if mediums sold out in the first week, the true demand was higher than the sales show.

A brand sold a core tee last season. Here is what its data showed, in units.

The net kept column is the starting curve. Medium sold out in week three, so its real demand was higher than 370. The brand raised medium in the next buy and trimmed extra large and double extra large, where returns for fit were high relative to units kept. It also reviewed the size chart for extra large, because those returns suggested the fit ran large.

Notice that no rate or price is needed for this. Unit counts and return reasons are enough.

Your store knows what sold. Your warehouse knows what came back, why, and what is still on the shelf. Both are needed for a good curve.

• Inventory by SKU, visible in your dashboard, shows which sizes are running low before they sell out.
• Monthly return reports with reasons by SKU show which sizes come back for fit.
• Weekly reporting from your account manager covers inventory status alongside service levels and shipping costs.
• Accurate counts are the foundation. A curve built on counts that drift is a curve built on bad data. See apparel inventory accuracy.

Drops

For a limited drop, a slightly conservative curve on the edge sizes avoids leftovers, because there may be no restock to sell them through. See planning a streetwear drop.

Restocks

For a restock, weight the curve toward the sizes that sold out first. See restocks.

Wholesale

Retailers often order in prepacks with a fixed size ratio. Keep that stock separate in your plan from the curve you sell direct. See allocating stock between DTC and wholesale.

• Copying last season’s buy without adjusting for sizes that sold out early. The curve repeats the shortage.
• Ignoring returns. Gross sales by size overstate the sizes customers order to try and send back.
• Using one curve for every style. An oversized hoodie, a fitted tee and a pair of boardshorts sell different curves.
• Building the curve from counts that drift. If the warehouse count is wrong, so is every decision built on it.
• Forgetting the edge sizes in a restock. A restock weighted only toward the middle leaves small and extra large customers waiting longer than they should.

The fix for most of these is the same: review sales, sell-out dates and returns by size after every season and every drop, and write down what you changed and why. The next buy gets better each time.

If you want a second pair of eyes on the data, ask your account manager for return reasons by SKU for the styles you are about to reorder. They work on site and can pull the returned items for you to look at. We are here. We got you.