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Min-Max Inventory Level Calculator

Enter daily demand, lead time, safety stock and review period to get the min and max inventory levels.

How it is calculated

Enter average daily demand (units per day), supplier lead time (days), safety stock (units) and the review period (days between stock checks). The tool computes two levels:

Min = demand × lead time + safety stock

Max = demand × (lead time + review period) + safety stock

The minimum is the reorder point: the stock at which an order must go out so that, over the lead time, you consume only the working stock and still keep the safety stock. The maximum is the ceiling that covers the lead time plus one review interval. Both results are rounded to whole units. Safety stock and review period are optional and count as 0 when left empty; with no review period the max equals the min. Demand and lead time are required, and none of the values may be negative.

Worked example

An item sells 40 units a day, the supplier needs 7 days, you hold 100 units of safety stock, and you review stock every 14 days.

  1. Demand during lead time: 40 × 7 = 280 units.
  2. Min = 280 + 100 = 380 units.
  3. Max = 40 × (7 + 14) + 100 = 840 + 100 = 940 units.

When stock drops to 380, place an order; it should bring you back toward 940 units.

Try this example →

Common mistakes

  • Mixing time units, such as demand per day with a lead time in weeks. Demand, lead time and review period must all use days, otherwise the levels are wrong by a factor of seven.
  • Using peak demand instead of the average. The safety stock field is meant to absorb spikes; entering the peak as daily demand double-counts the buffer and inflates both levels.
  • Leaving the review period empty and then reading the max as a ceiling. With no review period the tool treats it as 0, so max and min come out equal.
  • Treating the max as an order quantity. It is the stock ceiling; the amount to order is the max minus the stock you actually have when the order is placed.
  • Ignoring rounding. Fractional demand is rounded to whole units at the end (47.5 shows as 48), so small items with low demand may need a manual check.

About this calculator

The min-max inventory method sets a reorder point (the "min") and a ceiling (the "max") for stock. The minimum is (average daily demand × lead time) + safety stock — the point at which a new order must be triggered so stock doesn't run out before the replenishment arrives. The maximum adds coverage for the review period on top of that.

Once inventory falls to the min, an order is placed to bring stock back up to the max; safety stock absorbs demand spikes or supplier delays without triggering a stockout. Purchasing and warehouse teams use this framework as a simple, rule-based alternative to more complex demand-forecasting systems.

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Comments (1)

  • Editorial team

    The result is only as good as the demand figure you feed it. Use an average over a period that reflects normal selling, since a promotion or seasonal peak inflates both levels and ties up cash in stock. The tool cannot know how reliable your supplier is, so if deliveries are often late, raise the safety stock instead of padding the demand. Rounding is to whole units. How do you set safety stock for your items?

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