Guide · reviewed October 2026

What is a size curve?

50 XXLs. Nobody asked.

A size curve is how you split an order across sizes, based on what customers actually buy. An even split usually leaves the smallest and largest sizes on the shelf.

The formula

Worked example

300 units of one style: even split vs an example curve:

In our example, an even split sold 198 of 300 and left 102, mostly XS and XXL. This curve is an example; yours depends on your customer and category.

Worth knowing

• Build your curve from your own sales by size, ideally across a few styles and seasons.
• Use different curves for different fits and categories: unisex, women's, men's, waist sizes, shoes.

Common mistakes

• Ordering the same number of every size because the MOQ was a round number.
• Using one curve for every category.

Questions

What if I have no sales history?

Start from a typical curve for your category, buy carefully, and update it after your first few weeks of sales.

Should I cut sizes to hit an MOQ?

Sometimes it's better to drop the slowest size than to spread the minimum too thin.

Does OptiSKU build size curves?

Yes. The Sizes tab splits your order by a typical curve or by your own sales, and shows the stock you'd be left with from an even split.

Sources

• Mathematics for Retail Buying (Fairchild Books) · Bette K. Tepper and Newton E. Godnick
  The standard textbook for retail math: markup, margin, IMU, markdowns and open-to-buy.
• Ronnie Fieg on Kith's 15-Year Evolution (September 2026) · Complex
  Kith's founder on buying to an 85–90% sell-through target and reported margins on brands it buys wholesale.

Checked October 2026. Rates and rules change; confirm duty and tariffs with a licensed customs broker. All sources

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