Assortment Planning for Footwear Brands: Size Runs, Core Styles, and Buy Depth

What footwear assortment planning is

Footwear assortment planning is the process of deciding which styles, colorways, and size runs a footwear brand will offer each season — at what pair depth, through which channels, and with what split between core carryover styles and seasonal drops — while accounting for the size-run economics that make footwear buys structurally different from apparel buys.

The planning frameworks are familiar: an open-to-buy sets the financial envelope, an assortment plan selects the line, a buy plan converts it to purchase orders, and allocation moves pairs to doors and warehouses. What changes in footwear is the unit of decision. An apparel planner adds a style-color and picks up a handful of size SKUs. A footwear planner adds a style-color and picks up an entire size run — and every downstream calculation inherits that multiplier.

Why size runs change the assortment math

A men's run from size 7 to 13 in half sizes is 13 SKUs. Add a second width and it doubles. A women's run from 5 to 11 in half sizes is the same order of magnitude. In practice, one style-color commitment is really a commitment to 8–15 size SKUs, each of which needs its own depth, its own replenishment logic, and its own place in the allocation plan.

That multiplier compounds quickly across a line:

| Line shape | Style-colors | SKUs at a 13-size run | |---|---|---| | 10 styles × 2 colorways | 20 | 260 | | 20 styles × 3 colorways | 60 | 780 | | 30 styles × 3 colorways | 90 | 1,170 |

Three consequences follow:

• →Breadth is more expensive than it looks. Adding "just one more colorway" adds a full run of pairs, a full curve to forecast, and a full set of size-level allocation decisions.
• →Depth is not a number, it is a curve. "Buy 600 pairs" is meaningless until it is spread across sizes. Two style-colors with identical total depth can have completely different risk profiles depending on how the pairs are curved.
• →The minimum viable buy is a complete run. A style-color you cannot afford to stock as a full, saleable size run at launch is usually a style-color you should not carry — a partial run converts poorly from day one.

This is why footwear assortment reviews should be run in pairs at the style-color level with the size curve visible, not in units at the style level with sizing deferred to "later."

Build size curves from sell-through, not receipts

The most common curve-building error is averaging last season's receipts by size and calling it a demand curve. Receipts reflect what the brand bought, not what customers wanted. If size 10 sold out in week three, receipt-based curves will understate 10s forever — the brand keeps under-buying the exact sizes it keeps selling out of.

A sound curve is built from sell-through corrected for stockout periods: what sold by size while the full run was actually available, with stocked-out weeks excluded or demand-adjusted. The sell-through rate by size, not the receipt mix by size, is the planning signal. The size curve allocation formula covers the mechanics of spreading a buy across a curve; the size curve glossary entry covers how curves are constructed and maintained.

One curve is never enough. Curves should be specific to:

• →Category — running shoes, boots, and sandals curve differently; a brand-level average curve is wrong for all of them
• →Gender — men's and women's runs have different shapes, not just different size ranges
• →Channel — wholesale door demand and DTC demand rarely share a curve; a curve built from blended data misallocates both

In RetailNorthstar, curves are built from sell-through history at the style-color-size level and applied per category, gender, and channel — so the curve used at buy time is the same curve used at allocation time, rather than two versions living in two spreadsheets.

Split core from seasonal — they are different planning problems

Most footwear lines divide into two populations that deserve different math:

Core styles carry over season after season. They earn replenishment logic: a stable, well-evidenced size curve, weeks-of-supply targets, reorder triggers, and continuous size-level fill-rate monitoring. The planning question for core is not "should we buy it" but "how do we keep the run complete at the lowest inventory cost."

Seasonal drops are one-shot bets. They launch, sell through, and exit. There is no reorder window on most seasonal buys — tooling and production lead times close it — so the initial depth decision is the whole decision. Seasonal styles should be planned with more conservative depth, curves borrowed from the closest analogous core or prior-season style, and an explicit exit plan.

Blending the two in a single spreadsheet forces the same math onto both — usually replenishment-style thinking applied to drops that can never be replenished, or one-shot depth bets applied to core styles that should simply be kept in stock. Splitting the line into core and seasonal before setting depth is one of the highest-leverage structural changes a footwear planning team can make.

Size buy depth against MOQ and tooling constraints

Footwear buys have a floor that apparel planners rarely face at the same severity: factory MOQs and tooling economics. Lasts, molds, and outsole tooling carry long lead times and real cost, and factories quote minimums per style-color — sometimes per size tier — that the demand forecast does not care about.

That produces a recurring planning collision: the forecast says a colorway deserves 250 pairs, and the factory minimum is 600. The honest options are limited:

• →Drop the colorway and concentrate depth in the colorways that clear the minimum on merit
• →Consolidate — fewer colorways per style, or shared materials across colorways, to aggregate volume against the same tooling
• →Negotiate the minimum, usually by committing across seasons on core styles
• →Take the inventory risk knowingly — buy to the MOQ, plan the markdown exposure explicitly, and treat the overage as a cost of testing the style

What a planning team should not do is let the MOQ silently become the forecast. When the buy quantity is set by the factory floor rather than the demand plan, that gap needs to be visible in the open-to-buy — it is committed inventory risk, and it should be reviewed as such in the OTB plan.

Broken size runs and full-price sell-through

A size run "breaks" when its core sizes sell out while edge sizes remain. The remaining pairs still count as inventory, but they behave differently: shoppers who cannot find their size do not buy an adjacent one, so a broken run converts a fraction of the traffic a complete run does, and the leftover edge sizes drift toward markdown.

This is the mechanism by which footwear brands end a season with both stockouts and excess at the same time on the same style-color. The run broke early; demand went unmet in core sizes while edge-size pairs aged.

Managing broken-run risk is mostly a depth and allocation discipline:

• →Curve the initial buy honestly — under-curving core sizes is the fastest way to break a run in week two
• →Protect core-size depth on core styles with replenishment, even if edge sizes are allowed to sell down
• →Rebalance across doors and channels before marking down — a run broken in one door may be completable from another door's residuals
• →Watch size-level fill rate, not style-level sell-through — style-level numbers look healthy right up until the run is broken

Full-price sell-through in footwear is largely a function of how long runs stay complete. Markdown planning that ignores run integrity treats the symptom, not the cause.

Wholesale prebooks vs DTC drop depth

Footwear brands selling through both wholesale and DTC are running two different demand games with one inventory pool.

Wholesale prebooks provide a confirmed demand signal before the buy is placed. The buy for the wholesale channel is prebook volume plus a planned at-once reserve — a forecasting problem with a hard evidence base. The size curves come from door-level history, and the risk is concentrated in the at-once assumption.

DTC drops have no prebook. Depth is a forward bet built entirely from the brand's own sell-through history — which is also the channel where that history is richest, at the style-color-size level, if the brand actually uses it.

The failure mode for blended brands is planning both channels from one pooled number: wholesale demand quietly absorbing the pairs that were meant to protect DTC drop depth, or DTC curves applied to wholesale doors with very different size profiles. Channel-specific depth targets and channel-specific curves, reconciled against a single open-to-buy, are the fix — which is a data-model problem before it is a process problem.

A connected planning model vs spreadsheets

Everything above — curves by category and channel, core/seasonal splits, MOQ-constrained depth, run-integrity monitoring — is workable in spreadsheets for a small line. It degrades fast as the line grows, because footwear's SKU multiplier hits spreadsheet mechanics directly: 90 style-colors is over a thousand size-level rows per season per channel, and the size curve ends up copied across the OTB file, the buy file, and the allocation file, drifting in each.

A connected model — OTB → assortment → buy → allocation on one style-color-size data model — changes what the team can see:

• →The same curve flows from assortment plan to purchase order to door allocation, so the plan you approved is the plan you bought
• →Pair depth vs MOQ gaps are visible at buy time, inside the OTB, instead of being discovered in the factory's order confirmation
• →Run integrity is monitorable in-season at the size level, so rebalancing happens before markdown
• →Channel depth is reconciled against one inventory pool, so wholesale and DTC stop planning against each other

This is the workflow RetailNorthstar runs for mid-market and emerging footwear brands evaluating a move off spreadsheets: the same connected planning model proven on apparel lines, applied to a category whose style-color-size structure it already speaks natively. The footwear industry page covers the platform fit in detail.

Related resources

• →Footwear Brands — RetailNorthstar — Platform fit for footwear planning teams
• →Assortment Planning Platform — How the assortment module works
• →OTB Planning — The financial envelope for the buy
• →Size Curve Allocation Formula — Spreading a buy across a size curve
• →Sell-Through Rate Formula — The core performance signal for curve building
• →Size Curve — Glossary — How size curves are built and applied