Inventory glossary

What is Par level?

Par level is the stock quantity you want to have on hand for a SKU at all times.

Par levels give you a simple rule for restocking without doing math every time. You set the number once based on how fast an item sells and how long it takes to get more, then you just watch for when you dip below it.

This works best for steady, predictable products. If sales swing a lot by season or promotion, a fixed par level stops being accurate and you need to update it more often or switch to a method that adjusts with demand.

Formula

Par level = Average daily sales x (Lead time + Days between orders) + Safety stock

Example

A candle shop sells 6 lavender candles a day. The supplier takes 5 days to deliver, the owner orders once a week (7 days), and keeps 10 units of safety stock. Par level = 6 x (5 + 7) + 10 = 82 units. At each weekly order, the owner orders enough to bring stock back up to 82.

Common mistakes

  • Setting a par level once and never updating it as sales change.
  • Using the same par level for all SKUs instead of basing it on each item's own sales speed and lead time.
  • Ignoring case pack sizes, so the reorder quantity to reach par does not match what the supplier actually ships.

Par level and SteadyShelf

SteadyShelf tracks average daily sales and each supplier's lead time per SKU, so it can flag when a variant is likely to fall below its par level and suggest an order-by date to stay stocked.

SteadyShelf is launching on the Shopify App Store. Join early access to get the install link first.

Related terms

Reorder point · Safety stock · Min max inventory · Average daily sales · Lead time

Full inventory glossary

FAQ

How is par level different from reorder point?

They are closely related. Reorder point is the trigger quantity that tells you when to place an order. Par level is the target quantity you want to return to after reordering. Many small stores use the same number for both.

How often should I update par levels?

Review them when sales speed or supplier lead times change noticeably, such as a new season or a new supplier. For most small stores, checking every few months is enough unless something major shifts.

Let SteadyShelf do this math for every SKU

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