If you run a café and order weekly, the question you're asking is the right one: how do you set PAR levels and reorder points using last week's sales data? Most generic inventory advice was written for retail, where weekly sales are stable, items don't spoil, and "min/max" works fine. A café is different on all three counts.
This guide walks café operators on a weekly order cycle through the math, a worked example, the cadence, and the structural reason most café PAR systems drift within a quarter.
Quick answer
For a café ordering once a week, PAR level and reorder point per ingredient are computed from your last 30 days of POS sales (broken into daily buckets), with adjustments for perishability and demand variability:
PAR = (daily consumption rate × 7) + safety stock + decay adjustment
ROP = (daily consumption rate × lead time in days) + safety stock
You compute consumption rate by summing across every recipe that uses the ingredient, weighted by how often each recipe sells. Safety stock is a statistical buffer: z × σ × √7, where z is your service-level z-score (1.28 for 90% confidence, 1.65 for 95%) and σ is the standard deviation of daily demand. For perishables — which is most of a café's inventory — you also add a decay term that accounts for what spoils before you can sell it.
All of this can happen inside a closed-loop procurement platform — meaning a system that watches POS sales, computes the math on a schedule, and surfaces a recommendation for review. You stop guessing. The rest of this article walks through the math by hand for operators who want to see it.
A worked example: setting PAR for whole milk
Let's set the PAR level for whole milk at a café that orders weekly.