Stock Planning Simulator
Deciding when the shelf looks empty is always too late on a long lead time. The decision point arrives while stock still looks comfortable — and a marketplace stockout costs the ranking, not just the week.
Enter your sales rate and lead time; the tool computes the reorder day, the stockout date and the order quantity.
Order by
in 11 days
Stock runs out on day 60. With a 35-day lead time, the decision point is 11 days away.
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How it's calculated
The tool projects demand day by day: it takes your 30-day average and compounds it with the monthly growth you enter. Assuming a flat daily rate always puts the stockout date too late on a growing product.
The reorder point is the quantity you'll sell across the lead time plus safety cover — computed at the demand rate for that window, not as a flat number.
The suggested quantity covers the lead time plus another month and never drops below your MOQ. The goal is comfort until the next order, not a year of stock — tied-up cash is a cost too.
What people most often forget
- Lead time isn't production time. It's production plus freight plus customs plus receiving plus going live. Counting only production is how sellers end up two weeks late.
- Seasons and promotions break the average. Ordering at the normal rate before a peak is the classic way to run dry mid-campaign.
- Safety cover is insurance, not cost. Rank takes weeks to win back, and ads cost more throughout.
- Your supplier plans too. Quoted lead times stretch in busy periods; move pre-season orders earlier.
- Partial shipments are an option. Air-freighting the first tranche often costs less than the stockout you're avoiding.
Scope, sources and freshness
Demand is modelled as a smoothly growing curve; seasonality, promotional spikes, supplier delays and variant-level depletion are out of scope. Run it per variant on multi-variant products — total stock can look healthy while one size is already gone.
Sources last reviewed: 16 August 2026
Frequently asked
What is a reorder point?
The stock level at which you must order to avoid running out before the new batch lands: demand across the lead time plus safety cover.
How much safety cover do I need?
It depends on lead-time variability and demand volatility. Seven to ten days can be enough with a reliable supplier and steady sales; twenty-one is reasonable ahead of a season.
Where do I get the growth rate?
Compare the last three months. If sales are falling, enter a negative number — the tool handles it and will show stock lasting longer.
What's the harm in over-ordering?
Tied-up cash — plus storage fees and long-term storage surcharges in FBA. The goal is not running out, not filling the warehouse.
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