Some products are used up. Coffee, pet food, skincare, vitamins, filters, printer ink, cleaning supplies, contact lens solution: the customer buys, finishes and must buy again. At that moment, they either return to you, buy from somewhere else or forget and run out. A reminder at the right time makes the first outcome more likely, and it feels like service, not marketing.
Replenishment emails are among the most dependable flows for stores with consumable products, and among the easiest to get wrong, usually by sending on a generic schedule. This guide explains how to estimate the reorder date, build the trigger, write the message and measure the result. It builds on the post-purchase flow, win-back campaigns and customer lifetime value.
Which products suit replenishment
| Product type | Fit | Notes |
|---|---|---|
| Consumables with predictable use (coffee, pet food, filters) | Excellent | Usage time can be estimated from size |
| Health and beauty (skincare, vitamins) | Good | Usage varies by person; follow regulations on health claims |
| Household supplies | Good | Often bought in bulk elsewhere; price sensitive |
| Fashion basics (socks, underwear) | Moderate | Replacement cycles are long and irregular |
| Durables | Poor | Use accessories and complementary products instead |
| Seasonal items | Calendar-based | Use the season, not days since purchase |
Estimate the reorder date
There are three ways to estimate when a customer will run out, in rising order of accuracy.
- Product logic. A 250 g bag of coffee used at 15 g a day lasts about 16 days. A 30-day supply of vitamins lasts 30 days. Set a usage period for each product or variant.
- Observed repeat intervals. Look at customers who bought the same product twice and compute the median time between orders. This reflects real behaviour, including stockpiling and delays.
- Individual patterns. For customers with several orders, use their own typical interval.
Start with product logic, check it against observed intervals and adjust. If the median reorder interval is 38 days for a product that lasts 30, then most customers reorder after running out, and a reminder at day 24 to 27 should help. If it is 28 days, many reorder before running out and the reminder should be earlier or unnecessary for them.
| Product | Pack size | Estimated use | Reminder timing |
|---|---|---|---|
| Coffee 250 g | 250 g | About 16 days | Day 12 to 13 |
| Dog food 5 kg | 5 kg | About 28 days for one medium dog | Day 22 to 24 |
| Face serum 30 ml | 30 ml | About 60 days | Day 50 to 52 |
| Water filter | 1 filter | About 90 days (manufacturer guidance) | Day 80 to 82 |
| Multipack of 3 | 3 x pack | Multiply by 3 | Adjust by quantity |
The figures are examples. Use the manufacturer’s guidance or your own data, and take quantity into account: a customer who bought three bags will not need coffee in 13 days.
Build the trigger
- Store a replenishment period in days for each product or variant, as a metafield or in a table.
- On each paid order, calculate the expected run-out date for each line item as order date + period x quantity.
- Schedule the reminder for a set number of days before the run-out date.
- Before sending, check that the customer has not reordered the same product since, that the product is in stock and that they are subscribed to marketing.
- Send an email that names the product and links to a pre-filled cart or a one-click reorder.
- Record the send, and follow up once if there is no action.
The checks in step four prevent the embarrassing reminders: telling someone to reorder what they bought again last week, or promoting an item that is out of stock. Our email and SMS marketing flows service builds this logic on Klaviyo, Shopify Flow and other platforms.
Write the message
| Element | Example | Note |
|---|---|---|
| Subject | Time to restock your coffee? | Name the product |
| Preview | Reorder in one click | Describe the action |
| Opening | Your 250 g Ethiopia Natural should be running low about now. | Plain and specific |
| Product block | Image, name, size, price, button | Show what they bought, with the same variant |
| Option | Prefer to skip reminders? Choose how often you want to hear from us. | Respect preferences |
| Subscription offer | Or never run out: subscribe and we will send it every 4 weeks. Pause or cancel any time. | Optional and clear |
| Help | Using it more or less than we estimated? Tell us. | Feedback improves the timing |
Subscriptions: an offer, not a trap
Subscribing automates replenishment entirely, and many customers like it. But it is also a place where stores earn complaints and regulatory attention if cancellation is hard or terms are unclear. Present subscription as a convenience, show the price, frequency and next charge date, make it easy to pause, skip or cancel, and send a reminder before each shipment if the rules in your market require it. Do not push customers into subscriptions through confusing checkboxes. Reminders and subscriptions can co-exist: customers who prefer control get the reminder, and customers who prefer convenience subscribe.
Multi-item orders, gifts and edge cases
Real orders are messier than the model. A basket with five different consumables produces five run-out dates, and five emails would be absurd. Group reminders: wait for the earliest date, then list everything due within the next week or two in one message, with a single button to add them all. Orders placed as gifts should not trigger reminders to the buyer for the recipient’s use; flag gift orders at checkout and exclude them. Customers who have an active subscription should be excluded from reminders for the same product. Returns and refunds should cancel the pending reminder. B2B or bulk orders need different timing, since a restaurant buying 20 bags of coffee will not follow the household cycle. Review these exceptions after the first month by reading the complaints and the unsubscribes; they usually point to the rule you forgot.
| Case | Handling |
|---|---|
| Several consumables in one order | One grouped reminder, timed to the earliest run-out |
| Gift order | Exclude from reminders |
| Active subscription | Exclude that product |
| Returned or refunded item | Cancel the reminder |
| Bulk or B2B purchase | Separate flow or manual account management |
| Product discontinued or reformulated | Suggest the replacement, with a note about the change |
Timing and testing
- Test the lead time: a few days before, on the date and a few days after the estimated run-out.
- Test a second reminder after a week or so, with a different angle, such as a bundle or a free-shipping threshold.
- Segment by quantity bought and by customer: first-time buyers behave differently from loyal ones.
- Include a way to adjust the interval, and use responses to improve estimates.
- Keep the flow short. Two emails is typical, with a sunset rule for those who never respond.
Measure incremental repeat sales
Some customers would have reordered without a reminder. To find the real effect, hold back a random 10 to 20 percent of eligible customers and compare repeat purchase rate and revenue per customer over the following weeks. Look also at the effect on timing: a reminder may bring forward an order that would have happened anyway, which is still valuable if it prevents a lapse. Report reorder rate, revenue per recipient, unsubscribe rate and subscription conversions. See RFM segmentation for ways to target different customer groups.
A worked example
A coffee store has 4,000 customers on a 28-day cycle. Before the flow, 38 percent reorder within 45 days of a purchase. It adds a reminder at day 21 with a one-click reorder, holds out 10 percent and finds that in the next 45 days 46 percent of the recipient group reorder against 39 percent of the holdout. The lift is 7 percentage points. For 3,600 recipients that is about 252 extra orders, at $24 and a 45 percent margin, roughly $2,700 of extra margin per cycle. A small portion of customers, about 6 percent of those reminded, choose the subscription, which improves retention further. The numbers are illustrative; the holdout gives you the true lift.
Mistakes to avoid
- One timing for every product.
- Reminding customers who have already reordered.
- Ignoring quantity when calculating run-out.
- Making subscription the only way to reorder.
- No exit. Offer preference controls and a sunset rule.
- Making health claims in reminders without approved wording.
Sources and further reading
Figures and rules in this guide come from the primary pages below. Platform limits and prices change, so open the page before you build on a number.
- Klaviyo Help Center: flows and timing, building time-delay and conditional flows
- FTC: Restore Online Shoppers’ Confidence Act, US law on online subscriptions and negative option offers
- Shopify Help Center: subscriptions, selling subscriptions on Shopify