When to use it
Use it when a supplier order is coming up and you need to rank SKUs by urgency instead of guessing from units on hand.
Reorder Quantity Calculator for Ecommerce Sellers
Use this reorder quantity calculator when you have a spreadsheet of ecommerce SKUs and need a purchase review list. It estimates how many units to reorder after accounting for current stock, incoming stock, demand, lead time, safety stock, and supplier minimum order quantity.
Single-SKU calculator
How the calculation works
Formula used
Target stock level = average daily demand x (lead time days + review period days) + safety stock. Suggested reorder quantity = target stock level - inventory position, rounded up to MOQ.
Required CSV fields
At minimum, include sku, current_stock, lead_time_days, and a demand source. incoming_stock, minimum_order_quantity, and review_period_days make the recommendation match your buying cycle.
Input fields explained
| Field | Why it matters |
|---|---|
| sku | Identifies the product in the result CSV. |
| current_stock | Shows how many units are available now. |
| incoming_stock | Subtracts purchase orders already on the way from the suggested reorder quantity. |
| average_daily_sales | Sets the demand rate used for target stock and days left. |
| lead_time_days | Controls how much demand must be covered while waiting for replenishment. |
| minimum_order_quantity | Rounds the recommendation to a quantity your supplier will accept. |
| review_period_days | Sets how many days of demand to replenish after lead time; defaults to 30. |
Worked example
A mug sells 4.5 units/day, lead time is 21 days, review period is 30 days, safety stock is 31 units, current stock is 32, incoming stock is 0, and MOQ is 48. Target stock level = 4.5 x 51 + 31 = 261 units. Suggested reorder quantity rounds up to 240 units.
Common mistakes
- Ordering from current stock alone without checking incoming_stock.
- Forgetting supplier MOQ and ending up with a quantity the supplier will not accept.
- Using revenue instead of units sold for average_daily_sales.
When not to rely on the result
Review cash limits, warehouse space, supplier caps, promotions, and seasonality before turning a suggested quantity into a purchase order.
FAQ
Is suggested reorder quantity the same as reorder point?
No. Reorder point decides when to order. Suggested reorder quantity estimates how many units to order.
Does incoming stock reduce the recommendation?
Yes. Incoming stock is included in inventory position, so open purchase orders reduce the suggested reorder quantity.
Can I calculate quantities for many SKUs?
Yes. Upload the CSV calculator and export a result CSV for purchasing review.