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Par level & reorder point calculator
Par level = average daily usage × (lead time + order cycle + safety buffer). For oat milk used at 5 L a day with a 3-day delivery lead time, a 3-day order cycle and a 1-day buffer, that is 35 L, with a reorder point of 20 L. The calculator below does it for any item and shows the working, so you can put the number straight onto a par sheet.
Load an example
Your inputs
Your par sheet numbers
Par level
35 L
the level you top back up to
Reorder point
20 L
place the order at or below this
Suggested order now
24 L
4 cases of 6 (raw need 23 L)
Days of cover left
2.4
at current daily usage
The formula, with your numbers substituted
Par level = 5 × (3 + 3 + 1) = 35 L
Reorder point = Avg daily usage × (Lead time + Safety buffer)
Reorder point = 5 × (3 + 1) = 20 L
Suggested order = Par level − Stock on hand
Suggested order = 35 − 12 = 23 L → rounded up to 4 × 6 = 24 L
How do you calculate a par level?
A par level is the amount of an item you want on the shelf immediately after a delivery lands. It has to cover three separate stretches of time: the days you wait for the order to arrive (lead time), the days until you next place an order (order cycle), and a cushion for the week volume runs hot or the truck comes late (safety buffer). Multiply the total of those days by what you get through in an average day and you have your par.
Reorder point = Avg daily usage × (Lead time + Safety buffer)
Suggested order = Par level − Stock on hand
Days of cover = Stock on hand ÷ Avg daily usage
What does a worked example look like?
A cafe goes through 5 litres of oat milk a day. Its distributor delivers 3 days after the order is placed, the cafe orders twice a week (a 3-day cycle), and the owner wants a 1-day buffer because Saturdays run hot.
- Par level: 5 × (3 + 3 + 1) = 35 L
- Reorder point: 5 × (3 + 1) = 20 L
- With 12 L on hand: order 35 − 12 = 23 L, rounded up to 4 cases of 6 = 24 L
- Days of cover at 12 L: 2.4 days — below the 4-day reorder point, so this order is already late
Two practical notes. First, always round the suggested order up to a whole case; suppliers do not split them and a part case in your head becomes a short delivery on the shelf. Second, set par per item, not per category. Oat milk and whole milk share a fridge but rarely share a usage rate, and averaging them is how cafes end up 86ing the oat flat white at 10am on a Sunday.
Frequently asked questions about par levels
What is the par level formula?
Par level = average daily usage × (delivery lead time + order cycle + safety buffer), where every term after the multiplication sign is measured in days. For oat milk used at 5 L a day with a 3-day lead time, a 3-day order cycle and a 1-day buffer, the par level is 5 × (3 + 3 + 1) = 35 L.
What is the difference between a par level and a reorder point?
The par level is the quantity you top back up to when you order. The reorder point is the quantity that triggers the order in the first place. Reorder point = average daily usage × (lead time + safety buffer), so it excludes the order cycle. In the oat milk example the par is 35 L but the reorder point is 20 L — you place the order when you hit 20 L, and you order enough to get back to 35 L.
How big should my safety buffer be?
One to two days for reliable local suppliers, and three or more for anything that ships or that has ever short-delivered you. The buffer is priced insurance: each extra day of buffer adds one day of average usage to the money sitting in your stock room. For a fast-moving, cheap item like milk, a generous buffer costs almost nothing. For a slow, expensive item, keep it tight.
How do I work out average daily usage without a system?
Count the item on the same weekday two weeks running, add anything delivered in between, and divide the difference by the number of days. Usage = (opening count + deliveries − closing count) ÷ days elapsed. Do it across a full week rather than a Monday-to-Wednesday window, because weekend volume in most cafes is 30–50% higher than midweek and a short sample will set your par too low.