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Inventory Runway Calculator
See how many days of stock you have left — and when to reorder.
Your numbers
Stock on hand, sales pace, and your supplier lead time.
Units / day
%
Demand uplift
days
days
Buffer cover
Days of stock remaining
Reorder in 142d173days
Suggested reorder qty
682
Adjusted daily sales
22.0
with growthGet warned before you stock out
Connect your store and the Captain watches runway on every SKU and flags reorders before a bestseller runs dry.
How it’s calculated
Days of stock = Units in stock ÷ adjusted daily sales
Adjusted daily sales = average daily sales × (1 + expected growth%). Reorder when days of stock ≤ lead time + safety-stock days; suggested qty = adjusted daily sales × (lead time + safety-stock days).
Worked example
- Units in stock
- 3,800
- Adjusted daily sales
- 22 (20 + 10%)
- Lead time + safety
- 31 days
- Result
- Days of stock ≈ 173
Reorder in ~142 days, ordering about 682 units to cover the next lead time plus buffer.
What your result means
Inventory runway is how long your current stock lasts at your real sales pace — so you reorder before you run out, not after. The reorder timing builds in supplier lead time plus a safety buffer for spikes and delays. Run out of a bestseller and you lose both the sales and your hard-won rank.
Common mistakes
- Using flat average sales when demand is growing or seasonal — adjust the pace.
- Setting safety stock to zero, so any delay causes a stockout.
- Forgetting that lead times stretch around peak seasons and holidays.
Learn how it works
4 min guide
How to Calculate Inventory Runway (and Avoid Stockouts)
Inventory runway is how many days of stock you have left at your real sales pace. Learn the formula, how to factor in growth and lead time, and when to reorder so you never run out of a bestseller.
7 min guide
The E-commerce Inventory Planning Guide
Stock is cash on a shelf — and stockouts cost sales and rank. This guide covers the inventory numbers every merchant should track: sales velocity, reorder point, safety stock and inventory runway.
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Frequently asked questions
How do I calculate inventory runway?
Divide units in stock by your daily sales rate (adjusted for expected growth). That's how many days of stock you have; reorder before it falls below your lead time plus safety buffer.
How is runway different from a reorder point?
Runway is the time (in days) your stock lasts; the reorder point is the stock level that should trigger a new order. This tool gives you the runway plus a suggested quantity.
Last reviewed 31 Jul 2026 · reviewed by the Dash Captain team.