A size curve is the share of a style's units given to each size, based on how that style or category sells. A womenswear top might be bought 10% XS, 20% S, 30% M, 25% L and 15% XL.
Questo glossario è scritto in inglese.
A size curve is the distribution of units across sizes for a style, written as percentages or as a ratio. Brands use it to plan production and build prepacks, and retailers use it to split an order across sizes.
It is called a curve because units rise towards the middle sizes and fall away at the ends. Each category and customer has its own curve: denim, footwear and extended size ranges each follow different patterns.
Start from sales by size for similar styles over a full season, convert each size to a share of total units sold, and adjust for sizes that sold out early. A size that sold out understates its demand, so its true share is probably higher than the sales show.
A size run is the range of sizes a style comes in, such as XS to XL, and a size curve is how the units are spread across that range.
A brand plans 120 units of a T-shirt on a 10/20/30/25/15 curve across XS to XL. That gives 12, 24, 36, 30 and 18 units, which reduces to a 2-4-6-5-3 prepack of 20 units.
Brands use size curves to decide how many of each size to produce and to set prepack ratios, while retailers use their own curve to split each style's order across sizes.
A retailer's curve can differ sharply from the brand's because their customers differ. That is why buyers ask for open sizes, and why brands with several kinds of accounts often offer more than one pack.
One curve for every category
Knitwear, denim and dresses sell in different size patterns. Keep a separate curve for each category, and for each fit if you have several.
Building it from orders, not sales
Orders show what buyers expected to sell. Retail sell-through by size shows what shoppers actually bought.
Ignoring stockouts
A size that sold out in week three looks less popular than it was. Raise its share before you plan the next buy.
In ModaFlow your size curve becomes the size mix in your packs: you set the units per size once, and every buyer who orders the pack receives the same mix.
To see which sizes are really selling, work out sell-through by size with the sell-through calculator.
Aggiornato il 6 ottobre 2026
A prepack is a pack of one style that holds a fixed mix of sizes, and sometimes colors, sold as a single unit.
Sell-through rate is the percentage of the units a store received that it sold to shoppers within a set period.
Assortment planning is the process of deciding which styles, colors, sizes and quantities a store or brand will carry in a season, within a budget.
Open-to-buy (OTB) is the amount a retailer still has available to spend on new stock for a period, after allowing for planned sales, markdowns, the stock it already holds and the orders it has already placed.
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