Reorder Point Calculator
Calculate when to reorder inventory to avoid stockouts
Reorder Point Calculator tool
About Reorder Point
The reorder point is the inventory level at which you should place a new order to avoid stockouts. It accounts for demand during the lead time plus a safety stock buffer for uncertainty.
Formula:
Reorder Point = (Daily Usage × Lead Time) + Safety Stock
Reorder Point Calculator: key facts
- What it does
- Calculate when to reorder inventory to avoid stockouts
- Category
- Workplace Tools
- Cost
- Free, with no account, sign-up, or install.
- Your data
- Runs entirely in your browser — the files and text you enter are never uploaded to a server.
- Last reviewed
- . Report an incorrect result.
Understanding the Reorder Point Calculator
A reorder point is the inventory level that triggers a replenishment order. Order too late and you run out of stock — which means lost sales, emergency shipments, and unhappy customers. Order too early and you tie up cash in excess inventory that takes up shelf space and risks obsolescence. The reorder point formula finds the threshold that accounts for both the demand you will consume while waiting for the next order (demand during lead time) and a buffer for unexpected spikes in usage or delays (safety stock).
The formula is straightforward: Reorder Point = (Daily Usage × Lead Time) + Safety Stock. What makes it powerful is running the numbers precisely for each SKU rather than guessing. This calculator takes your three inputs, shows the full arithmetic, and optionally compares your current stock level against the result so you know whether you need to place an order right now. All calculations run locally in your browser.
Getting a result
- Enter your average daily usage — the number of units you typically consume or sell each day.
- Enter the lead time in days — how long it takes from placing an order to receiving it in your warehouse.
- Enter your safety stock — the buffer units you want to keep on hand beyond the lead-time demand to absorb uncertainty.
- Optionally, enter your current inventory level. If supplied, the tool compares it to the reorder point and flags whether you should place an order immediately.
- Review the formula breakdown and click "Copy Results" to capture the output for your purchasing records.
Demand during lead time, plus a buffer
The reorder point is the stock level at which a replenishment order should be placed. It is the quantity you expect to sell while waiting for delivery, plus a safety buffer for the times demand or the lead time runs above expectation.
Both inputs need to be in matching units of time. Daily usage against a lead time in days is the natural pairing; mixing a weekly usage figure with a lead time in days produces a result out by a factor of seven, which is the most common error here.
Safety stock is the judgement call. Set it to zero and you will stock out roughly half the time, since average demand is exceeded about half the time by definition.
- Selling 20 units a day with a 10-day lead time and 50 units of safety stock gives a reorder point of 250.
- Doubling the lead time to 20 days raises it to 450 — lead time drives the figure hardest.
- With no safety stock at all, the same case reorders at 200 and stocks out on any above-average week.
Reasons to use it here
- Full formula breakdown: the result panel shows the complete arithmetic — daily usage multiplied by lead time, plus safety stock — so you can verify the calculation or explain it to a colleague, not just read a number.
- Stockout alert: when you provide your current inventory, the tool highlights in red if you are below the reorder point and estimates how many days until stockout at the current usage rate, prompting immediate action.
- Green status confirmation: when current inventory is above the reorder point, the tool displays a green confirmation so you know no action is needed — avoiding unnecessary early orders.
- No formulas to memorize: the inputs map directly to the variables in the formula, with placeholder examples that make it clear what unit and scale each field expects.
Setting safety stock, and what this model assumes
Safety stock is a deliberate trade between the cost of holding inventory and the cost of running out. Holding costs are capital tied up, storage, insurance, and obsolescence; stockout costs are lost sales, expedited shipping, and customers who go elsewhere. The right buffer depends on which hurts more, which varies enormously by product.
A more rigorous approach sizes it statistically, from the variability of demand and of lead time and a target service level — the probability of not stocking out in a cycle. That requires the standard deviation of demand rather than just its average, which is why this simpler model asks you to supply a buffer directly rather than deriving one.
Three things the model does not capture. Seasonality, so a figure calculated from an annual average will be badly wrong in a peak — recalculate per season. Lead time variability, which is often the larger risk than demand variability, since a supplier's delay can be far more disruptive than a busy week. And minimum order quantities or price breaks, which frequently mean the economic order size differs from what the reorder point alone suggests.
Frequently Asked Questions
How do I determine the right safety stock level?
A common starting point is multiplying your maximum daily usage by your maximum lead time, then subtracting your average daily usage multiplied by your average lead time. This covers the worst-case demand spike during the longest possible replenishment wait. More sophisticated methods use the standard deviation of demand and lead time with a service-level z-score to hit a specific stockout probability target.
What if my lead time varies significantly?
If lead time is highly variable, use the maximum observed lead time in your calculation rather than the average. This produces a higher reorder point that errs on the side of safety. You can then reduce safety stock slightly to offset the increased lead-time estimate rather than stacking both the maximum lead time and a large safety stock buffer simultaneously.
Should I use daily or weekly units?
You can use any consistent time unit as long as usage and lead time match. If you measure usage per week, lead time must also be in weeks. Using days is the most common choice because lead times are typically quoted in days and daily movement data is usually available in inventory management systems.
