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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.

Units per day. From your POS or recent sales.
Volatility. Roughly 20–40% of consumption is typical.
Days between orders. Weekly = 7.
Days from placing the order to receiving it.
Probability of NOT stocking out per cycle.
For perishables. 0 for non-perishables.
Used to compute the order recommendation.
Optional fixed cushion on top.
139.5 units
Recommended PAR level · safety stock 13.5 · base demand 126
Order recommendation: 143.5 units
If your supplier has a pack size, round up to the next pack.
Show the math
Consumption rate18 units/day
Order frequency7 days
Lead time2 days
Risk horizon (max of freq, lead)7 days
Decay ratenone
Base demand over cycle126 units
Statistical safety stock (z × σ × √7)13.5 units
Manual buffer0 units
PAR level139.5 units
Current on-hand32 units
Plus lead-time consumption36 units
Order quantity143.5 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

  1. Pull your average daily sales from your POS for the last 30 days.
  2. Compute the standard deviation of daily sales (Excel: =STDEV.S(...)).
  3. Enter your order frequency and the supplier's lead time.
  4. Pick a service level. 90% is a sensible default; 95%+ for critical items.
  5. 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.

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