Size Run Ratios That Work: Avoiding Overstock in the Wrong Sizes

Here’s the truth every boutique owner learns the hard way: nothing drains profit faster than a back room full of the wrong sizes.

If you’ve ever realized mid-season that you’re sitting on four XLs, two larges, and not a single medium left on the floor, you already understand why size planning matters. This inventory disaster doesn’t just hurt sales — it ties up cash, uses storage space, and frustrates customers who walked in ready to buy.

That’s why getting your size run ratio right isn’t a nice-to-have. It’s survival.

Here’s exactly how to design your size run ratios from someone who’s made those mistakes and learned how to fix them using real sales data — not vendor recommendations or gut instinct.

Why Guessing Size Runs Kills Boutique Profit

Most small boutiques don’t fail because the product is bad. Instead, they struggle because the inventory mix is wrong.

When your size run ratio is off, three problems follow:

• Selling out of your fastest-moving sizes too early
• Losing customers when their size isn’t available
• Tying up cash in sizes that don’t move

Vendors love recommending balanced size runs. The problem? Their definition of balance has nothing to do with your customer base.

If your shoppers wear medium and large, ordering equal quantities of XS through XL guarantees overstock at the extremes. When you’re left with these XS and XL pieces at the end of a season, it doesn’t mean you’re underperforming — it just means you’re overbuying the wrong sizes.

What a Size Run Ratio Actually Is (And Why Yours Should Be Custom)

A size run ratio is the number of units you order in each size for a given style. It’s usually written as a short ratio — for example, 1–2–2–1 run means ordering 1 small, 2 medium, 2 large, and 1 XL.

The problem is that there is no universal correct formula. What works in one boutique may fail in another.

The right ratio is the one your customers actually buy.

Stop Trusting Vendor Ratios (Here’s Why)

Vendor-recommended ratios are designed to protect their margins — not yours. At first glance, they may seem reasonable, but they’re often:

• Based on national size-distribution averages.
• Modeled on big-box sell-through patterns.
• Built around full-size curves that don’t reflect boutique shoppers

If you’re running a small or mid-sized store, those assumptions don’t hold. Your customers are local. Your floor space is limited. Your cash flow matters more than filling every size slot.

Instead of relying on vendor ratios, you should build your own — based on sales behavior.

Size Run Ratios That Work for Small Boutiques

While every store is unique, independent boutiques often follow certain patterns.

Here are some starter tips:

• Skew toward mid-range for broad-appeal apparel: Order 1 small, 3 medium, 3 large, and 1 XL to match where most demand falls.

• Weight inventory toward core fits for trend-driven pieces: Allocate 1 small, 2 medium, 3 large, and 0–1 XL to limit risk while covering your strongest-selling sizes.

• Build depth in proven sizes for basics and repeat buyers: Stock 2 small, 3 medium, 3 large, and 1 XL to support consistent reorders and repeat demand.

Your purchase orders should always lean toward your top two selling sizes. Anything else is a gamble.

Use Early Sell-Through To Adjust Mid-Season

One of the biggest mistakes boutique owners make is locking into a bad ratio and riding it out for the entire season. This often means:

• Hoping the XLs sell eventually.
• Reordering evenly because it feels fair.
• Waiting too long to react.

But you don’t have to fall into these patterns.

After your first two to three weeks of sales, the data tells a clear story. The most successful owners listen. 

Point of sale (POS) reports help you adjust by:

• Doubling down on fast-selling sizes.
• Pausing reorders on slow movers.
• Redirecting your budget toward what customers want.

For example, if you see mediums selling through at 82% and XLs stuck at 14%, you can change your size run ratio to ensure you’re well-stocked for that style. 

Protect Cash Flow by Buying Fewer Sizes 

Carrying more sizes doesn’t equal better service if customers can’t find what fits. Every unsold unit is money you can’t reinvest. 

Tighter size runs mean more cash on hand, so you can:

• Reorder fast-moving styles quickly.
• Bring in new styles mid-season.
• Reduce forced markdowns on slow-selling sizes.

An effective ratio keeps cash available for growth, rather than sitting in unsold inventory.

Size Accuracy Equals Customer Satisfaction

Nothing frustrates loyal customers more than falling in love with a piece, only to realize taht it doesn’t come in their size. It’s one of the top complaints of modern shoppers, causing retailers to lose up to 23% of their profit to inaccurate sizing. 

When you stock the sizes your customers wear, they:

• Trust your assortment and sizing decisions.
• Return more often, knowing their size is available.
• Purchase with confidence and recommend your shop to others.

You don’t need every size for every style. You need the right sizes for your customers.

How To Refine Your Size Run Ratio Using POS Data

Most boutiques mismanage size availability because they lack visibility into their inventory. Real-time data supports a controlled inventory strategy, enabling you to make informed purchasing decisions that minimize waste and protect cash flow. 

A specialized boutique POS helps you:

• Track sell-through by size to see what moves
• Generate reorder insights from sales patterns
• Prevent future overstock by correcting imbalances early

Instead of relying on vendor ratios, you can build a tailored size run ratio based on actual store performance.

Turn Your Size Run Ratio Into a Profit-Earning Strategy

If you remember one thing, let it be this: size planning isn’t about fashion — it’s about cash flow.

Getting your size run ratio right reduces dead stock, improves customer satisfaction, and protects your boutique’s bottom line. 

Rain POS gives you the visibility to stop guessing and start buying with confidence — so you’re no longer stuck with the wrong sizes and empty racks where sales should be. 

Build and Price your custom setup today and see how Rain POS helps power smarter size planning and store growth.