When to reorder inventory on Shopify (with the actual formula)
Shopify tells you how much stock you have. It doesn’t tell you when to buy more. This is the one formula that answers that — explained for founders, not supply-chain analysts. No jargon, one worked example, and a table you can copy.
The formula
This is the whole thing. Everything below is just explaining the three numbers in it.
Reorder point = (average daily sales × lead time) + safety stock
Your reorder point is a stock level. When a product drops to that level, you place the order today — not next week. It’s set so the new delivery lands just before you would have run out.
The three numbers you need
How many units of this product you sell on a normal day. In Shopify: Analytics → Reports → “Sales by product variant SKU”, set the period to the last 90 days, then divide units sold by 90. Use 90 days, not 30 — one unusually good or bad week shouldn’t decide your buying.
How many days pass between placing your order and the stock being ready to sell. Count everything: production, shipping, customs, and the day it sits in your warehouse before it’s live. Ask your supplier for a real number instead of guessing — this is the number founders get most wrong.
Your buffer for when things go wrong — the supplier ships late, or you have an unusually good week. Keep it simple: average daily sales × a buffer in days. Use roughly 7 days for a Dutch supplier, 14 days for an EU supplier, and 21 days for an Asian supplier. Longer lead time, more that can go wrong, bigger buffer.
A worked example
Say you sell a chilli crisp that moves 12 units a day, and your supplier is in the Netherlands with a 14-day lead time. You pick a 7-day buffer.
- Safety stock = 12 × 7 days = 84 units
- Lead-time demand = 12 × 14 days = 168 units
- Reorder point = 168 + 84 = 252 units
So the day this product hits 252 units in Shopify, you place your order.
Now change only the supplier
Same product, same 12 sales a day. Only the lead time changes:
| Supplier | Lead time | Safety stock | Reorder point |
|---|---|---|---|
| Dutch / local | 14 days | 84 units | 252 units |
| Elsewhere in the EU | 30 days | 168 units | 528 units |
| Asia | 60 days | 252 units | 972 units |
This is the big one. The same product needs 252 units on the shelf with a Dutch supplier and 972 with an Asian one — nearly four times as much. Your reorder point is mostly about your supplier, not your product. It’s also why a single “low stock alert at 50 units” for your whole catalogue doesn’t work.
What it looks like for 10 products
This is the spreadsheet, filled in. Same formula on every row — only the sales, lead times and buffers change. Five of these ten need an order placed today.
| SKU | Sales/day | Lead time | Safety stock | Reorder point | In stock | Action |
|---|---|---|---|---|---|---|
| CHILI-CRISP-200 | 12 | 14 d | 84 | 252 | 310 | OK |
| CHILI-OIL-250 | 8 | 14 d | 56 | 168 | 140 | Order now |
| SAMBAL-150 | 5 | 14 d | 35 | 105 | 96 | Order now |
| TOTE-BAG | 2 | 14 d | 14 | 42 | 90 | OK |
| SOY-GLAZE-300 | 3 | 30 d | 42 | 132 | 400 | OK |
| NOODLE-KIT-2P | 15 | 30 d | 210 | 660 | 520 | Order now |
| GIFT-BOX-3 | 2 | 30 d | 28 | 88 | 150 | OK |
| SESAME-OIL-100 | 4 | 60 d | 84 | 324 | 300 | Order now |
| RICE-VIN-500 | 6 | 60 d | 126 | 486 | 700 | OK |
| CHOPSTICK-SET | 1 | 60 d | 21 | 81 | 60 | Order now |
Look at CHOPSTICK-SET: only 1 sale a day, but a 60-day supplier means you reorder at 81 units. And NOODLE-KIT-2P has 520 units in stock and still needs ordering today, because it sells 15 a day and takes 30 days to arrive. Neither is obvious by eye — that’s the point of doing the sum.
Four mistakes that cause stockouts
- Using the supplier’s promised lead time
Use what actually happens, not what the quote says. If the last three orders took 21 days rather than 14, your lead time is 21.
- One low-stock alert for everything
A single threshold across your catalogue ignores that products sell at different speeds and come from different suppliers. It’s the most common cause of running out.
- Forgetting stock already on order
Before ordering, subtract what’s already in transit — otherwise you double-order and tie up cash.
- Never updating the numbers
A reorder point based on last spring’s sales will run you out during a growth spurt or a seasonal peak. Redo it monthly.
OrderBee does this from your Shopify data
The maths above is genuinely simple. Doing it by hand every month, for every product, is what gets skipped — and that’s when you run out.
Connect your Shopify store and OrderBee runs exactly this calculation for every SKU, every day. Your average daily sales come straight from your order history (no CSV exports), you set each supplier’s real lead time once, and OrderBee tracks the reorder point, subtracts what’s already in transit, rounds to whole cases, and tells you the date you need to order by.
It also does the parts a spreadsheet can’t: it spots trends and seasonality instead of assuming a flat average, and it adds your wholesale and B2B sales from Moneybird, WeFact or CSV, so you buy for total demand rather than one channel.
If you’ve got a handful of products, one supplier and one channel, the spreadsheet genuinely is enough — build it and put 15 minutes in your calendar each week. It’s when your stock sits in more than one place, sells through more than one channel, or comes from several suppliers that doing this by hand stops being realistic.
Frequently asked questions
Reorder when your stock drops to your reorder point. The reorder point is your average daily sales multiplied by your supplier’s lead time in days, plus a safety-stock buffer. If you sell 12 units a day and your supplier takes 14 days, with a 7-day buffer your reorder point is (12 × 14) + 84 = 252 units. The day stock hits 252, you place the order.
Reorder point = (average daily sales × lead time in days) + safety stock. It answers one question: at what stock level do I need to order so that the new delivery arrives before I run out?
In Shopify go to Analytics, then Reports, and open “Sales by product variant SKU”. Set the period to the last 90 days and export it. Divide the units sold by 90 and you have your average daily sales per SKU. Use 90 days rather than 30 so one good or bad week does not distort the number.
Keep it simple: take your average daily sales and multiply by a buffer in days, based on how far away and how reliable your supplier is. Roughly 7 days for a Dutch or nearby supplier on a 14-day lead time, 14 days for an EU supplier around 30 days, and 21 days for an Asian supplier around 60 days. The longer the lead time, the more can go wrong, so the bigger the buffer.
No. Shopify tracks how much stock you have and can show low-stock levels you set by hand, but it does not calculate a reorder point from your sales history or your supplier lead times, and it does not tell you how much to order. You either do the maths yourself in a spreadsheet or use a forecasting tool.
Once a month is enough for most small brands, and 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 your sales are growing quickly, check monthly, because a reorder point based on old, lower sales will run you out of stock.