This calculator estimates when an ecommerce business should reorder inventory and how much safety stock can help absorb higher demand or longer supplier lead times.
How it works
It calculates regular lead-time demand, compares it with a maximum-demand and maximum-lead-time scenario, and treats the difference as a safety-stock buffer.
The formula
Inventory position equals on-hand stock plus incoming stock minus backorders. A position below the reorder point indicates a replenishment gap under the entered assumptions.
Worked example
With average demand 20 units/day, regular lead time 7 days, maximum demand 30, maximum lead time 10 days, the model gives 160 units of safety stock and a 300-unit reorder point.
This is a planning heuristic rather than a statistical service-level model. Seasonality, demand distributions, supplier reliability, minimum order quantities and multi-location inventory may require a more advanced model.
Frequently asked questions
What is the difference between safety stock and reorder point?
Safety stock is the buffer for uncertainty. The reorder point includes expected lead-time demand plus that buffer.
Does this calculator predict stockouts?
No. It estimates inventory thresholds from the assumptions entered; actual demand and supplier delays can differ.