What is the reorder point formula?

Reorder point = (average daily demand × lead time in days) + safety stock. The first part covers the demand you expect while an order is in transit; safety stock covers the demand you did not expect. This calculator normalises whatever units you type — demand per day, week or month, and lead time in calendar days, business days or weeks — to a daily basis before applying the formula, and shows the working for every row.

How do I calculate safety stock?

There are several accepted methods and this tool supports the common ones. Days of cover multiplies your daily demand by a buffer you choose. The demand-variability method is z × σ(demand) × √(lead time), where σ is the standard deviation of daily demand and z comes from your target service level. When lead times also vary, the fuller formula is z × √((lead time × σ(demand)²) + (daily demand² × σ(lead time)²)). You can also enter a fixed figure you have already agreed internally.

Which safety stock method should I use?

Use the simplest method your data supports. If you have no demand history, a fixed figure or a days-of-cover buffer is honest and easy to explain. Once you have a run of demand history, the variability methods size the buffer to how erratic that product actually is. Add lead-time variability only when your supplier is genuinely inconsistent — otherwise you will hold stock for a risk you do not have.

What service level should I choose?

A service level is the share of replenishment cycles the buffer is sized to cover, not a guarantee. 95% is a common starting point for regular lines, and the tool also offers 90%, 97.5% and 99% plus any custom figure between 50% and 99.9%. Higher service levels raise the buffer sharply, so it is normal to hold a high level for a few critical products and a lower one for the long tail.

How much demand history do I need?

Two observations are the mathematical minimum for a standard deviation, but a short history is easy to mislead yourself with. When you import fewer than eight periods, or when demand is highly irregular, the tool says so on the row rather than presenting the number as settled. Review promotions, closures and one-off bulk orders before you trust the average.

What is inventory position and why does it matter?

Inventory position is on-hand plus on-order minus committed stock. It is what you compare against the reorder point, because stock that is already on a purchase order will arrive to cover demand, and stock promised to a customer will not. Comparing on-hand alone to a reorder point is the most common reason for accidentally ordering twice.

Is my data uploaded anywhere?

No. CSV files are parsed in your browser and your table is saved only in this browser's local storage. No account, no email, and nothing about your demand, suppliers or stock levels leaves your device.

Free tool

Free reorder point and safety stock calculator

Work out when to reorder every product and how much buffer to hold. Enter demand and lead time in the units you already use, or import history and let the calculator do the statistics — free, no sign-up, all in your browser.

Products

Swipe the table sideways to see every column.

Reorder planning table. Edit demand, lead time and safety stock inputs for each product to see its reorder point.
	Product	SKU	Average demand	Lead time	Safety stock method	Safety stock input	On hand	On order	Committed	Reorder point	Status	Row actions
										100	Above reorder point
										—	Insufficient data
										—	Insufficient data

3 products1 calculated

Your table and settings are saved in this browser only — nothing is uploaded, and no account or email is needed.

House blend coffee beans (example)

COF-HB-1KG

Reorder point

100units

Above reorder point

position 14017.5 days of stock on hand

The inventory position is above the reorder point of 100 units.

Safety stock method

How this was calculated

Lead-time demand: 8 units/day × 10 days = 80 units
Safety stock: 20 units entered by hand
Reorder point: 80 + 20 = 100 units
After rounding: Rounded up to the next whole unit = 100 units

Compare the formulas

The same demand and lead time, sized with each safety-stock method.

Method	Safety stock	Reorder point
None	0	80
Manual	20	100
Days of cover	—	—
Demand σ	—	—
Demand + lead σ	—	—

A dash means that method needs an input this product does not have yet. These figures are a calculation, not purchasing advice — review supplier terms, cash and shelf life before ordering.

How to calculate a reorder point

1
Add the products you want to plan
Type them into the table, import a CSV, or bring them across from the SKU and barcode generators.
2
Enter demand and lead time
Use the units you already work in — per day, week or month, and calendar days, business days or weeks. Or import demand history and let the tool calculate the average and its variability for you.
3
Choose a safety stock method
Pick a fixed figure, days of cover, or a service-level method based on demand and lead-time variability. The comparison panel shows what each method would give for the same product.
4
Review the position and export
Add on-hand, on-order and committed stock to see which products have already reached their reorder point, then export a CSV with every input, the working and the result.

The formulas this calculator uses

Reorder point and safety stock formulas used by this calculator
Figure	Formula	When to use it
Reorder point	(average daily demand × lead time days) + safety stock	The level at which you place the next order.
Lead-time demand	average daily demand × lead time days	What you will sell or use while the order is in transit.
Safety stock — days of cover	average daily demand × buffer days	Simple, easy to explain, needs no history.
Safety stock — demand variability	z × σ(daily demand) × √(lead time days)	Sizes the buffer to how erratic demand is.
Safety stock — demand and lead-time variability	z × √((lead time × σ(demand)²) + (daily demand² × σ(lead time)²))	Adds inconsistent supplier lead times.
Inventory position	on hand + on order − committed	The figure to compare against the reorder point.

Standard deviations are calculated as sample standard deviations, because your history is a sample of past periods rather than every period that will ever happen. A reorder point is a calculation from the inputs you provide, not purchasing advice — check supplier minimums, cash and shelf life before you order.