Footwear profit is decided at size level, not at style level. Two boutiques can buy the same style at the same cost and end the season in completely different positions, because one bought the sizes its customers wear and the other bought the sizes the vendor packed. This guide is about that decision: what a size run is, how much depth to put behind each size, and how to learn your own curve instead of borrowing someone else's.
I am Carina Hatton, boutique owner since 2013 and ecommerce coach since 2019. There is no universal size distribution that applies to every store, and any article that gives you one is guessing. Everything below is method plus clearly labelled hypothetical examples.
Quick answer
What a size run actually is
A size run is the set of sizes a vendor ships together for one style, with a set quantity of each. Some terms you will hear:
| Term | What it means | Why it matters |
|---|---|---|
| Size run | The range of sizes offered in a style | Defines the sizes you can serve |
| Prepack or case pack | A fixed bundle of sizes and quantities set by the vendor | Decides your depth whether you like it or not |
| Size curve | The distribution of quantities across sizes | The thing you are trying to match to your customers |
| Open stock | Buying individual sizes rather than a fixed pack | More control, often higher cost or higher minimums |
| Broken run | A style missing its core sizes | Effectively stops selling even with pairs left |
Ask every vendor whether they sell prepack only, open stock, or both. It changes your entire buying approach, and the answer varies by brand and even by style within a brand.
How vendor prepacks work, and what they cost you
A prepack is convenient for the vendor and a compromise for you. It assumes an average customer base, which no individual store has.
A hypothetical eight-pair prepack:
- Size 6: 1 pair
- Size 7: 2 pairs
- Size 8: 2 pairs
- Size 9: 2 pairs
- Size 10: 1 pair
If your customer base skews larger, you will sell the 9s and 10s first and hold 6s and 7s for months. Buy the same prepack four times for four styles and you now own four unwanted size 6s across the floor. That is the quiet way footwear cash disappears.
Open stock solves this but usually carries a higher per-pair cost or a larger minimum. The trade-off is worth calculating: paying slightly more per pair for the right sizes is almost always cheaper than marking down the wrong ones.
Common size-range structures
The range you offer is a positioning decision, not just a buying one.
- Narrow core range: fewer sizes, deeper in each, simpler stock file, but you turn some customers away
- Full range: serves everyone, spreads the same budget thinner, harder to keep complete
- Extended range: a genuine differentiator if mainstream retail underserves those sizes locally, and usually harder to source
Whichever you pick, say it clearly on the site. A customer who discovers at checkout that their size is never stocked does not come back.
Full sizes and half sizes
Half sizes improve fit and reduce returns, and they double the number of stock-keeping units you carry per style. Some categories tolerate full-size-only far better than others:
| Category | Fit sensitivity | Practical approach |
|---|---|---|
| Sandals and slides | Lower, open construction forgives a little | Full sizes are often workable |
| Sneakers | High, customers know their exact size | Half sizes reduce returns meaningfully |
| Boots | High, and calf width matters as much as length | Publish shaft and calf measurements alongside size |
| Heels | High, comfort depends on precise fit | Half sizes where the vendor offers them |
| Flats | Moderate | Full sizes with a clear fit note usually hold up |
Deciding depth by size
Depth is how many pairs of one size, in one style, you commit to. The honest first-order answer is: take the vendor run, because you do not yet have data. The second-order answer is built from your own sales.
Size share = pairs sold in that size ÷ total pairs sold
Suggested units for next buy = planned run size × size share
Sell-through by size = pairs sold in that size ÷ pairs received in that size
A hypothetical: after a season you have sold 120 pairs across all styles, with this distribution:
| Size | Pairs sold | Size share | Units in a 12-pair run |
|---|---|---|---|
| 6 | 8 | 6.7% | 1 |
| 7 | 20 | 16.7% | 2 |
| 8 | 31 | 25.8% | 3 |
| 9 | 29 | 24.2% | 3 |
| 10 | 21 | 17.5% | 2 |
| 11 | 11 | 9.2% | 1 |
This is one hypothetical store's data, not a template. Another boutique in a different town with a different niche will produce a genuinely different shape, and that is the point.
One trap in this calculation
Sales data underreports sizes that sold out early. If you only received one size 9 and it sold in three days, the data says size 9 is 8% of sales when demand may have been triple that. Always look at sell-through by size alongside share of sales. A size at 100% sell-through was constrained by supply, not by demand, and deserves more depth next time.
Boots, sneakers, sandals and heels behave differently
- Boots carry the highest ticket and the longest season, so a broken run hurts more. Calf and shaft measurements are part of fit, not an extra detail.
- Sneakers have the most size-precise customers and benefit most from half sizes and quick reorders.
- Sandals have a short, sharp season and forgive slightly imperfect fit, so full sizes and shallower depth are often fine.
- Heels sell in bursts around occasions, which means lower overall depth but a real cost when the run breaks before the occasion season peaks.
Test buys before commitment
On a new style or a new vendor, buy the smallest run the vendor permits and treat it as a paid experiment. What you are testing:
- Whether your customer wants the style at all
- Whether the vendor's sizes run true for your customers
- How fast it sells at full price
- The return rate, if you sell online
Then reorder with depth once it earns it. The counter-instinct, which is to buy deep on a style you love, is the most expensive habit in footwear buying.
How to track size performance
You need size-level visibility, not just style-level. Practical setup:
- Create a separate product variant per size so every sale records the size
- Report weekly on units sold by size, across all styles and within each style
- Record which sizes sold out and how quickly, because that is your constrained-demand signal
- Log returns and exchanges by size, since a size with high exchange rates means the fit note is wrong
- Review the whole picture before every buying appointment, not after
The tracking basics are in boutique inventory management, and the calculation itself in sell-through rate for boutiques.
Reordering and keeping runs intact
The reorder that matters most is the one that fills the hole in a still-selling style. A hypothetical rule set:
| Signal | Action | Why |
|---|---|---|
| Core sizes sold out inside four weeks | Reorder those sizes immediately if available | Demand is proven and the season is still live |
| Style selling well but only extremes remain | Fill the middle sizes or plan a markdown | The style cannot convert without its core sizes |
| Even sell-through across all sizes | Reorder the whole run | The vendor curve fits your customer for this style |
| Slow across every size | Mark down, do not reorder | The style is wrong, not the sizing |
Ask vendors at the buying appointment how quickly they restock individual sizes. A vendor who can fill a single size in two weeks is worth more to you than one with a slightly better wholesale price and no mid-season restock.
What to do when only extreme sizes remain
Every season ends with a handful of 5s and 11s. Options, roughly in order of preference:
- Sell them online, where the audience is wide enough to contain those customers, even if the local store's is not
- Bundle or cross-merchandise so the odd size sits alongside something the customer came in for
- Mark down progressively rather than waiting for one end-of-season clearance
- Market to a size-specific list if you have collected sizes from past buyers
- Clear it and move on, because floor space and cash matter more than recovering the last few dollars
Check what each discount level does to the style's overall margin in the Markdown Calculator, and see the full profitability picture in wholesale shoe profit margins.
Why there is no universal size curve
Size distribution depends on who walks through your door, which is shaped by your location, your niche, your price point, your marketing and the style itself. A western boot store and a comfort sandal store in the same town will sell different curves. A boutique in one region will differ from an identical concept elsewhere. Even within one store, a trend sneaker and a classic bootie can sell different distributions.
That is why the method matters more than any number. Take the vendor run first, measure honestly, correct on the second buy, and keep correcting. After two or three cycles your own curve is more valuable than any published figure, because it describes your actual customers.
Half sizes, widths and how much complexity to take on
Every extra size option multiplies your inventory count without adding a single new style to the store. Half sizes and widths are the two places where footwear buyers most often take on more complexity than the business can carry.
| Decision | Case for | Case against |
|---|---|---|
| Carry half sizes | Better fit, fewer returns, strong loyalty in fitted styles | Roughly doubles the size count and the money tied up per style |
| Whole sizes only | Simpler buying, deeper stock per size, less leftover | Some customers cannot be fitted at all |
| Carry widths | Serves customers few stores serve, high loyalty | Multiplies again, and vendor availability is limited |
A workable middle path used by many small stores: carry half sizes only in the styles where fit is unforgiving, such as heels, dress flats and fitted boots, and stay on whole sizes for sandals, slides and relaxed casual styles where a little room does not matter. That targets the complexity at the place it earns something instead of spreading it everywhere.
Widths are worth considering only when you have heard the request repeatedly from real customers and found a vendor who supplies them reliably. A width offering that is out of stock most of the time is worse than not offering it, because it creates an expectation you cannot meet.
Prepack math, worked
Vendors sell many footwear styles as a prepack, a fixed bundle across sizes. The question is not whether prepacks are good or bad, it is whether this vendor's pack matches your customers. Here is how to answer it with numbers rather than instinct. All figures hypothetical.
Cost of forced units = units in sizes you would not choose x (landed cost - expected clearance recovery)
Open stock premium = (open stock unit price - prepack unit price) x total units
Choose open stock when the premium is lower than the cost of forced units.
Suppose a vendor offers a twelve-pair prepack at $28 per pair, or open stock at $31 per pair with a minimum. Your own sell-through data says two of the twelve pairs fall in a size that consistently clears at a deep discount for you, recovering about $20 per pair against a $28 cost.
- Cost of forced units across ten styles: 20 pairs x $8 lost = $160
- Open stock premium across the same 120 pairs: $3 x 120 = $360
In that example the prepack wins, and it is worth knowing rather than assuming. Change one input, though, and the answer flips. If the weak size clears at $12 instead of $20, the forced cost becomes $320, and if three pairs per pack fall in weak sizes it becomes $480 and open stock is clearly cheaper. This is why the calculation matters more than the general advice.
Two further points. First, the comparison only becomes meaningful once you have real sell-through by size, which is an argument for taking prepacks on a first order and reassessing later. Second, ask whether the vendor allows mid-season single-size reorders, because a vendor who does removes most of the downside of an imperfect pack. Minimum order mechanics are in minimum order quantity, and the clearance side in the Markdown Calculator.
Related: how to start a shoe boutique and shoe boutique assortment planning.