Use the output as a threshold, not a forecast.
A reorder point answers when to order; an order quantity answers how much. This simple model separates the two and includes stock already confirmed on purchase orders in the inventory position.
It is designed for stable products where a days-of-cover safety buffer is practical. Once a SKU has enough history, replace the simple buffer with demand and lead-time variability, service-level targets and seasonal forecasts.
Reorder point and order quantity
Lead-time demand equals average daily sales multiplied by lead-time days. Safety stock equals average daily sales multiplied by safety-stock days. Reorder point is their sum.
The suggested order brings inventory position up to demand expected across lead time, the next review period and the safety buffer. It then rounds the result upward to the entered supplier case pack.
At 8 units per day, a 21-day lead time consumes 168 units. A 14-day safety buffer adds 112, producing a reorder point of 280 units before open purchase orders are considered.
What this calculation does—and does not include.
Included in this model
- Average demand and lead time
- Safety stock
- Reorder point
- Case-pack-rounded order quantity
Not automatically included
- Probabilistic service-level optimization
- Supplier capacity risk not entered
- Seasonality outside your assumptions
- Working-capital constraints
Inventory formula model — demand/lead-time assumptions are user supplied
Reviewed 2026-08-23. Review dates describe the live model, not a guarantee that a third-party fee has not changed since.
Limitations to keep visible
- Average demand is not sufficient for highly seasonal, promotional, intermittent or fast-growing SKUs.
- Supplier minimum order values, multi-SKU container constraints, expiry and warehouse capacity are not modeled.
- Use usable inventory, excluding damaged, reserved or quarantined units.
Questions this calculator is designed to answer.
reorder point calculator
Calculate lead-time demand plus safety stock, then compare the reorder point with your current inventory position.
Compare safety-stock methods →reorder point formula
A simple reorder point combines expected demand during lead time with a safety-stock buffer.
Compare safety-stock methods →safety stock and reorder point calculator
Use a days-of-cover buffer for a simple planning model, then move to variability-based safety stock when the SKU has enough history.
Choose a safety-stock method →Frequently asked questions
Does stock on order reduce the need to reorder?+
Yes. Confirmed units on order are included in inventory position. Exclude unreliable or unconfirmed supply.
How many safety-stock days should I use?+
Choose a buffer based on demand volatility, supplier reliability, replenishment frequency and the cost of a stockout. Then back-test it against history.
Why is the order rounded up?+
Suppliers commonly require case packs or order multiples. Rounding up prevents an infeasible suggestion.