Reorder point calculatorwith safety stock
Enter your daily demand and supplier lead time to find the stock level that should trigger your next purchase order. Pick the safety stock method that matches the data you have.
The starting numbers are example values, not Spark data. Replace them with your own.
Reorder point
300units
Lead time demand
140
Safety stock
160
Reorder point = lead time demand + safety stock, rounded up to whole units.
The reorder point formula
Lead time demand plus a buffer
The reorder point is the inventory position at which you place the next order. Order at that level and the new stock should arrive just as the old stock runs down to your safety buffer.
Reorder point = (average daily demand × average lead time) + safety stock
For how much to order once you hit it, see how to calculate reorder quantities.
Worked example (illustrative numbers)
- 1. Lead time demand. A SKU sells 10 units a day and the supplier takes 14 days: 10 × 14 = 140 units.
- 2. Safety stock (max and average). The busiest normal day is 15 units and the slowest delivery took 20 days: (15 × 20) − 140 = 160 units.
- 3. Reorder point. 140 + 160 = 300 units. When available stock plus what is on order drops to 300, place the order.
The same SKU at a 95% service level, with a demand SD of 3 units and a lead time SD of 2 days, needs 38 units of safety stock and a reorder point of 178. The method changes the answer a lot, which is why the inputs matter.
Beyond the formula
Every input above is a guess. Spark measures it.
This calculator takes one average demand, one lead time and one variability number you estimate. Spark Inventory works out each of them per SKU and per warehouse from your own sales and purchase history, keeps them current as demand moves, and turns the result into a purchase order your team approves.
Demand rate
This calculator: One average you type in.
Spark: Demand ESP sorts every SKU as steady, trending, seasonal or intermittent, backtests several forecasting models on its own history and keeps the one that predicted best. The reorder point uses the forecast for the actual lead time window, not a flat average.
Stockout days
This calculator: Counted as low demand.
Spark: Sales lost while a SKU was out of stock are added back before forecasting, so a stockout does not teach the system to buy less.
Seasonality and new items
This calculator: Not modeled.
Spark: Seasonal curves per SKU. Items with less than a year of history borrow the seasonal shape of similar items, and new products start from look-alike items.
Promotions and events
This calculator: Not modeled.
Spark: Demand Calendar events and demand signals lift or lower the forecast for a set window, within bounds, and fade out after.
Demand variability
This calculator: A standard deviation you estimate.
Spark: Measured from the forecast’s own past misses over the lead time, so safety stock reflects how predictable each SKU really is. You set the target service level (95% by default).
Lead time
This calculator: One number for every order.
Spark: Learned from completed purchase orders per supplier, with lead time variability and on-time reliability tracked. Falls back to price book lead times by order size and supplier defaults when history is thin.
What counts as stock
This calculator: Whatever number you compare it to.
Spark: Inventory position: on hand plus open purchase orders and inbound transfers, less sales orders already committed by ship date.
How much to order
This calculator: Not covered.
Spark: Economic order quantity or days of cover, net of stock already on order and raised to the supplier’s minimum order quantity. Price breaks are compared across suppliers.
Locations
This calculator: One location.
Spark: Calculated per warehouse. Distribution centers plan for the stores they restock, and those stores get transfer proposals instead of purchase orders.
From number to purchase order
A reorder point is a trigger. Spark plans the buy.
Every number explained
Each reorder point comes with a breakdown of the forecast, lead time and safety stock behind it. Items with too little or too erratic history are flagged as low confidence instead of firing noisy alerts.
Reorder automation you control
A reorder rule sweeps every SKU and drafts one purchase order per supplier and warehouse. Run it in Observe, Propose or Autopilot mode, and switch it off or reschedule it from the Automation page.
Text with Sparki
Get a text when an item reaches its reorder point and approve the drafted purchase order with one reply. Included on Solo ($99/mo) and up.
Spark MCP
Ask Claude, ChatGPT or any MCP client what to reorder and why. Spark answers from your live stock, incoming supply and Demand ESP forecasts.
Reorder point FAQ
Reorder point and safety stock questions
What is the reorder point formula?+
Reorder point = (average daily demand × average lead time in days) + safety stock. The first part covers what you expect to sell while you wait for the order to arrive. Safety stock covers demand or delays above that average.
How do I calculate safety stock?+
Three common methods: max and average ((max daily demand × max lead time) − (average daily demand × average lead time)), service level (Z score × the combined variability of demand and lead time), and days of cover (average daily demand × the number of buffer days you want to hold). The service level method is the most precise when you have enough sales history to measure variability.
What is a good service level?+
Many businesses start at 95%, which means a 5% chance of running out during a given lead time. Fast movers and items that lose a sale when out of stock often justify 97.5% or 99%. Slow, costly or easily substituted items can sit lower. Higher service levels need disproportionately more safety stock.
Should I compare the reorder point to on-hand stock?+
Compare it to your inventory position: available stock plus units already on order, minus anything committed to open orders. Using on-hand alone can trigger a second order for stock that is already on the way.
Why does a fixed reorder point stop working?+
Demand and lead times change with seasons, promotions and suppliers, so a reorder point set once drifts out of date. Spark Inventory recalculates it per SKU and per warehouse with Demand ESP: a forecast chosen by backtesting each SKU’s own history, safety stock sized from that forecast’s past misses and real supplier lead times, and an order quantity that respects minimum order quantities. It then drafts the purchase order for a person to review.