Reorder point & safety stock calculator
Three numbers in, two numbers out: when to reorder, and how much buffer to hold. Free, no signup, nothing to install — the answer updates as you type.
Shopify → Analytics → Reports → “Sales by product variant SKU”, last 30 days.
Order placed → ready to sell. Use what actually happens, not what you were quoted.
How often you want to be in stock. 95% suits most brands.
Roughly — it sizes your buffer.
Order when stock drops to 205 units.
- Average daily sales
- 12 / day
- Sales during lead time
- 168 units
- Safety stock
- 37 units
- That’s about
- 17.1 days of cover
Assumes your supplier delivers on time. If yours is often late, add those days to the lead time above — that’s the simplest way to account for it.
We’ll send you the reorder-point template with the formulas already set up, so you can run it for your whole catalogue.
One email with the template. No newsletter, no sharing your address.
How the calculation works
Reorder point = (average daily sales × lead time) + safety stock
Your last 30 days of sales divided by 30. With 360 units sold, that’s 12 a day.
What you’ll sell while waiting for the delivery: 12 × 14 days = 168 units. Without this you’d run dry before the order lands.
Your buffer for the weeks that beat plan. It grows with your service level (95%), with how much your sales bounce around, and with the square root of your lead time — longer waits mean more that can go wrong. Here: 37 units.
Want the same maths walked through by hand, with a 10-SKU example? Read the full guide to when to reorder on Shopify.
Doing this for every product, automatically
This calculator handles one product at a time, with numbers you type in. That’s fine for a handful of SKUs — but the inputs change every week, and redoing it by hand is what gets skipped.
OrderBee runs this calculation for every SKU, every day, straight from your Shopify sales history — no typing. It uses each supplier’s real lead time, subtracts stock already in transit, rounds to whole cases, and tells you the date you need to order by. It also picks up trend and seasonality instead of assuming a flat 30-day average, and folds in wholesale and B2B sales from Moneybird, WeFact or CSV.
Frequently asked questions
Reorder point = (average daily sales × lead time) + safety stock. Average daily sales is your last 30 days of sales divided by 30. Safety stock is your service-level Z-score multiplied by the variability of your daily sales and by the square root of your lead time. In plain terms: enough stock to cover demand while you wait for the delivery, plus a buffer for the weeks that go better than planned.
For most small brands, 95% is the sensible default: you expect to be in stock for about 95 out of every 100 order cycles. Go to 98 or 99% for your bestsellers and anything customers will not wait for, and drop to 90% for slow movers where tying up cash hurts more than an occasional stockout. Higher service levels need disproportionately more stock, so do not put everything at 99%.
Safety stock is the buffer you hold on top of expected demand, to absorb the weeks you sell more than average or the deliveries that arrive late. Without it, any better-than-average week during your lead time turns into a stockout.
A buffer-in-days rule of thumb (for example, hold one week of extra stock) is quick but blunt: it ignores how much your sales actually bounce around and what risk of stocking out you are willing to accept. This calculator sizes the buffer from your sales variability and your chosen service level, so it is usually more precise — often leaner for steady sellers and more generous for spiky ones. Both are reasonable; this one is better tuned.
Use the lead time that actually happens rather than the one you were quoted. If the last three orders took 21 days instead of 14, enter 21. That is the simplest and most reliable way to account for an unreliable supplier without needing extra statistics.
Once a month is enough for most small brands, plus after anything that changes demand or supply: a big promotion, a new sales channel, a seasonal peak, or a supplier changing their lead time. If you are growing quickly, check monthly, because a reorder point based on older, lower sales will run you out of stock.