How to Plan Reorders Before Your Bestselling Product Runs Out
Run out of your best product and you lose sales while you wait. Here is the simple arithmetic for when to reorder, with a worked example and a variant table.
The short answer: Reorder when your stock falls to the number of units you will sell while waiting for the next delivery, plus a cushion for delays. In short: reorder point = (units sold per day x lead time in days) + safety stock. If you sell 5 a day, your supplier takes 15 days and you want a 5-day cushion, you reorder when 100 units are left.
Last updated 28 October 2026.
Running out of your best seller is expensive in a quiet way. You do not see the lost sale; you just see an empty page, a customer who goes elsewhere and a few days of traffic you paid for or worked for that lands on "sold out". The fix is not a gut feeling that you are "getting low". It is a number you work out once per product and check regularly.
This guide walks through the standard method with one fully worked example, then shows how to adjust it for variants, promotions and cash limits. All the figures are illustrative; swap in your own.
The four numbers you need
1. Daily sales (your sales rate). How many units you sell per day on average. Use recent real sales, not a hopeful target. Take the last four weeks if sales are fairly steady.
2. Lead time. The full time from placing the order to having the units ready to sell. Count every step: the supplier's production time, transport to you, customs or clearing if relevant, and the time you take to check and label the goods. Shopify's guide defines lead time simply as how long it takes to get inventory from your supplier after you order it.
3. Safety stock. Extra units you hold in case the delivery is late or sales run faster than usual. The same guide describes it as the extra inventory you keep in case a shipment does not arrive within the expected lead time.
4. Reorder point. The stock level at which you place the next order. The standard formula is the same in the common inventory references: normal use during the lead time plus safety stock.
Keep the time units the same. If you measure sales per day, lead time must be in days, not weeks.
A worked example (illustrative)
Take a 250 g body butter. Everything below is made up to show the method.
Step 1: Find your daily sales
Units sold in the last four weeks:
| Week | Units sold |
|---|---|
| 1 | 32 |
| 2 | 38 |
| 3 | 35 |
| 4 | 35 |
| Total | 140 |
Check: 32 + 38 + 35 + 35 = 140. Four weeks is 28 days, so 140 / 28 = 5 units a day.
Count paid orders that were not cancelled. Cancelled orders return items to your stock, so they should not count as sales.
Step 2: Add up your lead time
- Supplier makes the batch: 8 days
- Delivery to you: 6 days
- Your checking and labelling: 1 day
Check: 8 + 6 + 1 = 15 days.
Step 3: Work out demand during the lead time
5 units a day x 15 days = 75 units. If you reorder with 75 units left and nothing changes, the new batch arrives just as you sell the last one. That is too tight, which is why safety stock exists.
Step 4: Choose your safety stock
There is a statistical method (it uses the spread of your daily sales and a service-level factor), and it is worth learning if you have a lot of data. For most small sellers, a plain method works well enough: base the cushion on how late deliveries actually run.
Look at your last few deliveries. Suppose the last three took 15, 17 and 20 days. The longest was 5 days later than your usual 15. Safety stock = 5 days x 5 units a day = 25 units.
Step 5: Add them together
Reorder point = 75 + 25 = 100 units.
Does it hold up?
Walk through the timeline:
- You place the order when stock reaches 100.
- On a normal delivery (day 15), you will have sold 75, leaving 25. The new batch arrives and you carry on with 25 as a cushion.
- On the slowest delivery you have seen (day 20), you will have sold 5 x 20 = 100. Stock is 0 on the day it arrives. Tight, but you did not run out before it came.
The method is working if the worst delay you have recently seen does not empty the shelf. If a late delivery has never happened to you, still keep some cushion; the first time is usually the worst.
How much should you order?
The reorder point tells you when. Your order quantity is a separate decision about cash, storage and shelf life.
Suppose each unit costs you ₦3,200 and you want to cover about 30 days of sales:
- 30 days x 5 units = 150 units
- 150 x ₦3,200 = ₦480,000
If you can only afford 100 units, that is 100 x ₦3,200 = ₦320,000. With 100 units, the batch arrives on top of the 25 you still have, so you start at 125 and hit the reorder point of 100 again after about 5 days. In other words, you would be reordering every 20 days instead of every 30. That means more orders, more delivery costs and more admin, but less cash tied up. It is a trade-off, not a failure.
When a smaller, more frequent order costs more per unit, work the numbers in your profit per order. The guide to real profit per order and how to price products show how to see what a change in cost does to your margin.
Adjusting for variants
If the product comes in sizes, colours or scents, work out a reorder point for each one. The overall number can hide a problem: you may have 100 units in total but none of the best-selling scent.
Suppose the 5 units a day split 50%, 30% and 20% across three scents (illustrative):
| Variant | Units per day | Lead-time demand (15 days) | Safety stock (5 days) | Reorder point |
|---|---|---|---|---|
| Vanilla | 2.5 | 37.5 | 12.5 | 50 |
| Unscented | 1.5 | 22.5 | 7.5 | 30 |
| Lavender | 1.0 | 15 | 5 | 20 |
| Total | 5.0 | 75 | 25 | 100 |
Check: 2.5 + 1.5 + 1.0 = 5.0; 37.5 + 22.5 + 15 = 75; 12.5 + 7.5 + 5 = 25; 50 + 30 + 20 = 100.
Round to whole units when you order. Use the split from recent sales, and update it if one variant starts selling faster.
Adjusting for promotions and seasons
The formula assumes the next 15 days look like the last 28. They will not always. If you plan a promotion, a festive season or a big social post, raise the daily sales rate before you calculate.
Suppose you expect a 40% lift in sales:
- Daily sales: 5 x 1.4 = 7 units
- Demand during lead time: 7 x 15 = 105
- Safety stock (5 days): 7 x 5 = 35
- Reorder point: 105 + 35 = 140
Check: 105 + 35 = 140. In that case your old trigger of 100 would be too late. Be conservative with the lift; it is a guess. If you are not sure demand will rise, ordering a large amount for a promotion is risky. The guide to testing demand before buying stock covers how to check first, and the busy sales period checklist covers the rest of the preparation.
Short lead times change the picture
A local supplier who delivers in 3 days needs a much lower trigger. For the same sales rate of 5 a day and a 2-day cushion:
- Demand during lead time: 5 x 3 = 15
- Safety stock: 5 x 2 = 10
- Reorder point: 15 + 10 = 25
Shorter lead times mean less stock tied up, which is one reason a nearby supplier can be worth a slightly higher unit price.
Practical rules that keep the number honest
- Count what you can actually sell. Exclude damaged items, held items and units promised to a customer. If you sell in several places, see how to prevent overselling, because your real available stock may be smaller than the shelf count.
- Include stock already on order. If a batch is on its way and you reorder again by mistake, you will overbuy. Many sellers compare "stock on hand plus stock on order" against the reorder point.
- Recalculate each time. After every delivery, update the sales rate and the lead time you actually experienced.
- Do the sum for your top few products only. Start with the ones that make most of your money, not the whole catalogue.
- Note the shelf life. For food, skincare and anything that expires, a big cushion can turn into waste. Cap the order size by how fast it sells.
Where an online store helps
On the website side, Webift tracks stock per product or per variant, lets you set a low-stock threshold, and shows an in stock, low and sold out view along with inventory counts on the dashboard. A useful habit is to set each product's low-stock threshold to the reorder point you calculated, so that "low" in the inventory view means "time to reorder", not an arbitrary number.
To be clear about the limits: this is a threshold you set yourself. Webift does not predict demand, and nothing here claims an automatic reorder. Webift will email you once when an order takes a tracked item down to its low-stock level (you can switch this off in notification settings) and lists low items on your dashboard, but you still place the supplier order yourself. A notebook with the reorder point written next to each product works just as well.
A short checklist
- Daily sales from the last four weeks (paid, non-cancelled orders)
- Lead time written step by step, including your own checking time
- Safety stock from the longest recent delay x daily sales
- Reorder point = (daily sales x lead time) + safety stock
- One reorder point per variant for products with sizes or scents
- Reorder point raised before a promotion, not after
- Order quantity checked against cash and shelf life
- Reorder point updated after every delivery
If you want a store that shows low-stock items and lets you set the threshold per product, you can create a Webift store. It is a convenient place to keep the number, not a forecasting tool.
Frequently asked questions
What is the reorder point formula?
Reorder point = (average daily sales x lead time in days) + safety stock. The first part is the stock you expect to sell while waiting for delivery; the second is the cushion for late deliveries or faster sales.
How do I calculate safety stock without statistics?
Look at your longest recent delay beyond the usual lead time and multiply the extra days by your daily sales. If a delivery that normally takes 15 days once took 20, the extra 5 days at 5 units a day gives 25 units. Larger businesses use statistical formulas, but this approach is a sensible start.
How many days of stock should I keep?
There is no universal number. It depends on your lead time, how reliable the supplier is, how steady your sales are, how much cash you have and whether the product expires. The reorder point is the better question: at what stock level do I place the next order?
What if my sales are unpredictable?
Use a larger safety stock for products with uneven demand, review the numbers more often, and order smaller batches if you can. If a product is new and you do not yet know its true sales rate, treat the calculation as a first estimate and update it after a few weeks of real orders.
Should I reorder based on the total or per variant?
Per variant, wherever customers choose between sizes, colours or scents. Totals can look healthy while your best-selling variant is already gone.
