Visualize the inventory reorder cycle — reorder point, order-up-to level, demand and lead-time variability — and watch it respond live.

How the reorder point calculator works

This free inventory reorder point visualizer models a single product under a continuous-review (s, S) inventory policy — the same reorder-point logic that ERP systems like Fishbowl use to time purchase orders. The solid line is your on-hand inventory, which drains at your daily sales rate. When it falls to the reorder point (s), the model places a purchase order — shown as a dot on the line and a bar sized to the order quantity. Those units are now on order and arrive after the lead time, lifting on-hand back toward the order-up-to level (S). That repeating rise and fall is the inventory reorder cycle. (The model tracks what's already on order, so a long low stretch doesn't fire duplicate POs while the first is still in transit.)

What is a reorder point?

A reorder point is the inventory level that triggers a new order. The classic reorder point formula is average daily demand × lead time + safety stock. Set demand, lead time, and safety stock below and the chart shows exactly when each order fires and whether it arrives before you run out.

Quantity-based vs. time-based (days of cover)

• Quantity-based reorder point fixes s and S as unit levels — the flat reference lines on the chart.
• Time-based (days of cover) sets them as days of demand. Each day the model looks back over your window at the realized sales rate and converts days into units, so the reorder-point and order-up-to lines flex as demand drifts.

Safety stock and service level

Safety stock is the cushion the reorder point holds beyond expected lead-time demand to absorb variability in sales and delivery times. Raise demand or lead-time standard deviation and watch the service level fall — the tool quantifies the stock-out risk of thin safety stock.

Covering sell-through during lead time

Turn on Cover sell-through to order extra on top of each PO — the units you expect to sell while the order is in transit — so replenishment refills up to S and replaces what drains during the wait. The teal segment stacked on each order bar is that added buffer.

Frequently asked questions

How do you calculate a reorder point?

Multiply your average daily demand by the replenishment lead time, then add safety stock: reorder point = demand rate × lead time + safety stock. The visualizer runs this continuously against seeded, variable demand so you can see how the formula holds up day to day.

What is the order-up-to level (S)?

The order-up-to level is the target inventory position each order refills to. The difference between S and the reorder point s is roughly your order quantity — a larger gap means fewer, bigger orders.

What is days of cover?

Days of cover is how many days your current stock will last at the recent sales rate. Setting the reorder point in days of cover (instead of fixed units) lets it adapt automatically as demand rises or falls.