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Min/Max Inventory Calculator

Set the minimum and maximum stock levels that drive periodic-review ordering.

Min/max is the workhorse of periodic-review replenishment: two numbers per item, set once, that let a storekeeper order correctly without doing any arithmetic. The min is the trigger. The max is the ceiling you top up to. The gap between them is your normal order size.

Minimum level

Raise a replenishment order once stock reaches this level.

Maximum level
Typical order quantity

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Your numbers

units/day
days
days

How often you actually look at this item and raise orders.

units

The formula

Min = (Demand × Lead time) + Safety stock · Max = (Demand × (Lead time + Review period)) + Safety stock

Order the difference between max and current position whenever stock falls to min.

What it means

Reorder Point — full definition

Read in the glossary

How to use it

  1. 1

    Set the min exactly as you would a reorder point — lead-time demand plus safety stock.

  2. 2

    Add the review period to the max. If you only review this item fortnightly, the max must carry you through those extra 14 days as well.

  3. 3

    Order up to max from your inventory position — on-hand plus on-order — not from on-hand alone.

Where it goes wrong

  • Shortening the review period is usually cheaper than raising the max. Reviewing weekly instead of monthly cuts the required ceiling substantially on every item at once.

  • Min/max levels left unchanged for a year become the reason you hold dead stock. They encode last year's demand until someone updates them.

Worked example

Fortnightly review on a 7-day lead time

40 units a day, 7-day lead time, 14-day review cycle and 80 units of safety stock gives min = (40 × 7) + 80 = 360 and max = (40 × 21) + 80 = 920. Normal order size is 560 units. Move to weekly review and the max drops to 640 — roughly 280 fewer units of standing inventory for the cost of one extra look per fortnight.

Common questions

When is min/max better than reorder point plus EOQ?

When you review on a fixed cycle rather than continuously, when many lines ship from one supplier, or when the people raising orders are storekeepers rather than planners. It trades a little efficiency for a lot of simplicity.

Should min and max differ by location?

Yes. Both depend on local demand and local lead time, so a shared pair across branches will always be wrong at both ends.

What if the order quantity is below the supplier minimum?

Raise the max until the gap clears the MOQ, or consolidate the item into a multi-line order with the same supplier.

Let AWRA do this on your live data

This calculator works on one set of numbers. AWRA OpsHub keeps min/max inventory calculator results current across every item, supplier and location — automatically.