PAR Level Calculator
Free, in-browser. The same formula LineNow uses internally — base demand plus statistical safety stock, with optional decay-rate adjustment for perishables. Nothing leaves your machine.
Show the math
| Consumption rate | 18 units/day |
| Order frequency | 7 days |
| Lead time | 2 days |
| Risk horizon (max of freq, lead) | 7 days |
| Decay rate | none |
| Base demand over cycle | 126 units |
| Statistical safety stock (z × σ × √7) | 13.5 units |
| Manual buffer | 0 units |
| PAR level | 139.5 units |
| Current on-hand | 32 units |
| Plus lead-time consumption | 36 units |
| Order quantity | 143.5 units |
The formula
LineNow's PAR level uses three components:
PAR = baseDemand + (z × σ × √orderFrequency) + manualBuffer
For non-perishables, baseDemand is just consumption rate × orderFrequency. For perishables (decay rate d > 0), baseDemand integrates the exponential decay of inventory across the order cycle:
baseDemand = (s/d) × (s^(−T) − 1) × c where s = 1 − d, T = order frequency days, c = consumption rate
The order recommendation is PAR − onHand + (consumption rate × lead time), ensuring you have enough to cover both the order cycle and the lead-time gap before the next delivery.
How to use this
- Pull your average daily sales from your POS for the last 30 days.
- Compute the standard deviation of daily sales (Excel:
=STDEV.S(...)). - Enter your order frequency and the supplier's lead time.
- Pick a service level. 90% is a sensible default; 95%+ for critical items.
- For perishables, enter a decay rate (see decay rate by category).
Computing PAR for one item is a useful exercise. Computing it for 200 items every night, with consumption pulled from your POS automatically, is what LineNow does. Free for 90 days, $50/month after.