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Shopify Reorder Calculator

The Shopify Reorder Calculator estimates when to place a replenishment order and how many units to buy. It combines average daily sales, supplier lead time, safety stock, current inventory, and stock already on order into a practical inventory recommendation.

This is useful for merchants managing products with steady demand who want to reduce both stockouts and excess inventory. The calculator reports a reorder point, the number of days until inventory reaches that point, and a suggested order quantity based on a target coverage period.

Inventory assumptions

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Result
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Suggested reorder quantity
Reorder point—
Days until reorder point—
Inventory position—
Target inventory—

1. Calculate average daily sales
Use a recent representative period and divide units sold by the number of selling days.

2. Enter supplier lead time
Measure from placing the purchase order until stock is available for sale.

3. Choose safety coverage
Add buffer days for demand variation or supplier delays.

4. Enter inventory position
Provide available units and any confirmed units already on order.

5. Review timing and quantity
Place the order when inventory position approaches the reorder point, subject to supplier minimums and cash constraints.

Formulas:

Reorder point = Average daily sales × (Lead time + Safety days)
Suggested order quantity = max(0, Target inventory − Inventory position)

Inventory position equals current available stock plus units already on order. Target inventory equals average daily sales × target coverage days.

What the result means

The suggested quantity raises inventory position to the chosen target coverage, while the reorder point indicates when replenishment should be triggered.

Seasonality, promotions, minimum order quantities, case packs, and supplier reliability are not automatically forecast.

Given: Average sales are 8 units per day, lead time is 21 days, safety coverage is 10 days, current stock is 350 units, no units are on order, and target coverage is 45 days.

Calculation: Reorder point = 8 × (21 + 10) = 248 units. Target inventory = 8 × 45 = 360 units. Inventory position = 350 units. Suggested order = 360 − 350 = 10 units. Days until reorder point = (350 − 248) ÷ 8 = 12.75 days.

Result: Suggested reorder quantity = 10 units.

The current stock is still above the trigger, but it is expected to reach the reorder point in about 12.8 days.

Should pending purchase orders count as inventory?

Include confirmed units that are likely to arrive as planned. Exclude uncertain or delayed quantities until their status is reliable.

How many safety-stock days should I use?

Choose a buffer based on demand volatility and supplier reliability. Fast-moving or unpredictable products generally require more protection than stable products.

What if average daily sales are zero?

The tool cannot estimate timing from zero demand. Review whether the product is new, seasonal, or inactive and use a forecast if appropriate.

Does this account for minimum order quantities?

No. Round the suggested quantity up to the supplier minimum or case-pack size, then assess the cash and storage effect.

How often should I update the inputs?

Update them whenever sales velocity, lead time, promotions, or supplier performance changes materially. High-volume products may need frequent review.