How to use this calculator
- Enter or choose average daily usage.
- Enter or choose supplier lead time.
- Enter or choose days between orders.
- Enter or choose safety stock.
- Enter or choose stock on hand.
- The quantity to order now updates as you type. Use Copy result or Share to keep it.
Method
Reorder point = Daily usage × Lead time + Safety stock; Par level = Daily usage × (Lead time + Days between orders) + Safety stock; Order = ⌈Par level − On hand − On order⌉ (not below 0)
- Daily usage
- average units used per day
- Lead time
- days from placing an order to receiving it
- Safety stock
- buffer kept for demand spikes and late deliveries
Worked example
- Reorder point = 40 × 5 + 60 = 260 units.
- Par level = 40 × (5 + 7) + 60 = 540 units.
- Order = 540 − 180 − 100 = 260 units.
Using 40 units a day with a 5-day lead time and a weekly order, order 260 units now to bring stock back to the 540-unit par level.
What the result means
Order the suggested quantity at each review. If you keep running out, raise the safety stock or shorten the order cycle; if stock expires on the shelf, lower the par level for that item.
Assumptions and limits
- Usage and lead time are steady at the averages entered.
- Safety stock is set by you; no statistical service level is assumed.
- Pack sizes, minimum order quantities and expiry dates are not considered; round to whole packs yourself.
Questions
How much safety stock should a clinic keep?
Enough to cover the worst realistic mix of higher usage and late delivery. Critical items usually get a larger buffer than routine consumables.
What is a par level?
The stock you top up to at each order. It covers usage until the next delivery after the next order, plus safety stock.