Reorder point = lead-time demand + safety stock
Days of stock uses available stock divided by daily demand. Suggested order quantity uses lead time, coverage period, safety stock and the inventory position, with a minimum of zero.
04 · Business planning
Inventory Reorder Calculator
Estimate how long your stock will last, when to reorder and how much to buy. A quick check for one SKU using a simple model.
Enter stock parameters
CALCULATORPlanning results
RESULTEnter your stock parameters
Results include estimated days of stock, reorder point, suggested order quantity and assumptions to review.
How it works · Single-SKU model
Turn replenishment assumptions into a calculation you can review.
This deterministic model supports a quick discussion of one SKU. It helps business and development teams agree what demand, lead time and safety stock mean before building a system.
Use real data from a consistent time window
State whether daily demand uses a 7-day, 30-day or seasonal window. Lead time should include production, transport, inspection and receipt, rather than only shipping days in a contract.
Add variability, incoming stock, minimum orders and warehouse constraints
A production inventory system also needs promotions, seasonality, minimum orders, incoming and reserved stock, returns, batch expiry and transfers. Keep a calculation snapshot for each suggestion.
Limitations
This model does not evaluate demand variance, service levels, shortage costs or working capital. Zero demand, variable lead times and perishable goods need a more suitable model and review by the responsible person.
Designed and maintained by the Jianxu Digital technical team · Updated July 27, 2026