Start at the variant level
Review each size separately. A product-level unit total cannot tell you which sizes remain available.
Shopify size inventory guide
How to catch broken size runs before “in stock” becomes misleading.
Shopify inventory totals can look healthy while the sizes customers buy most are already gone. This guide explains how apparel and footwear teams can monitor size-level inventory, identify fragmented assortments, and focus replenishment attention where it matters.
The core problem
Product-level inventory hides the shape of the remaining assortment.
Imagine a shoe offered in sizes 6 through 12. The product may still show as available because sizes 6, 6.5, 11.5, and 12 remain. But if the sizes that drive most recent demand are 8, 8.5, 9, and 9.5, the style is commercially fragmented long before total inventory reaches zero. The same pattern appears in apparel across size, color, waist, length, width, band, cup, and other variants.
Measure recent demand by size
Calculate what share of recent orders each size represents instead of treating every size as equally important.
Compare stock with demand
Look for high-demand sizes with zero or low inventory, especially when slower sizes still carry meaningful units.
Prioritize exceptions
Focus planner attention on the products where size-level availability is most disconnected from recent demand.
Signals worth monitoring
Four checks are more useful than “total inventory remaining.”
- Recent demand share by size
- Current inventory by size variant
- Missing demand share
- Days of cover by important size
- Core-size availability
- Size + color fragmentation
- Repeated stockout exceptions
- Products still technically in stock
Manual Shopify workflow
You can audit a size run manually before adding any software.
Export or review recent order lines and current variant inventory. Group recent sales by product and size, calculate each size’s share of demand, then compare that mix with what is available now. Flag products where meaningful demand sits in unavailable or low-cover sizes. This works as a manual check; the challenge is repeating it consistently across a large catalog every day.
What is a broken size run?
A product whose important sizes are missing or at risk even though the style still has inventory overall.
Is a stockout alert enough?
Not always. A generic low-stock alert may miss whether the unavailable variant is a high-demand core size or a low-demand edge size.
Does this replace forecasting?
No. Size-run monitoring is an exception signal that helps teams see current assortment risk; it is not a full enterprise forecasting system.
Can SizeGuard automate the check?
Yes. SizeGuard reads Shopify inventory and recent demand, monitors size runs daily, and surfaces the exceptions that need attention.
Automate the daily check
SizeGuard turns the manual audit into a recurring Shopify signal.
Install SizeGuard for read-only size-level monitoring, or send us one public product first and request a free size-run check.
Ready to monitor size inventory?
SizeGuard is built for Shopify apparel, footwear, and other size-heavy catalogs.
Install on ShopifyPrefer to see the problem first? Request a free size-run check.