Most Shopify merchants who sell consumables lose a predictable slice of repeat revenue every month. Not because their products are bad, or because customers forgot — but because no one sent a reminder at the right moment.
The moment is specific. Too early and the customer still has plenty left; they ignore you. Too late and they have already ordered from a competitor or simply moved on.
The core calculation
Getting the timing right starts with one number per product: usage days.
Usage days = the number of days a single unit of the product typically lasts one customer.
For a 60-capsule supplement taken twice daily, that is 30 days. For a 100ml face serum used morning and night, it might be 45 days. For a 5kg bag of dog food fed to a 20kg dog, roughly 14 days.
Once you have usage days, the reminder formula is straightforward:
Send reminder on: purchase date + usage days − buffer daysA buffer of 2–3 days gives the customer time to act before they actually run out. For a 30-day supplement, send on day 27 or 28.
Why a fixed schedule fails
The common alternative is to send a single weekly or fortnightly email to all customers who bought a given product. This approach fails for two reasons.
First, customers buy on different dates. A batch email sent on a Tuesday will reach some customers on day 3 after their purchase and others on day 29. The day-3 customer is not interested. The day-29 customer might already be out of stock.
Second, not all products have the same usage cycle. If you treat a 14-day product and a 60-day product the same, you will be wrong for most customers most of the time.
Per-customer scheduling
The correct model schedules a reminder per order, per customer, based on:
- The date of the customer’s purchase
- The usage days configured for that product
Each customer gets exactly one reminder, timed to their own run-out date. There is no batch blast. There is no single send date applied to everyone.
This is exactly how Reorder Reminder Pro works. Merchants configure usage days per product (or use Auto Mode for a single global value), and the app schedules a reminder for each qualifying order automatically.
What to do if you do not know your usage days
Start with a conservative estimate. It is better to send slightly early than late — a prompt “just in case you’re running low” is useful. A prompt three weeks after they ran out is not.
For most consumables categories, typical starting values are:
| Category | Starting usage days |
|---|---|
| 30-serving supplements | 28 |
| 60-serving supplements | 58 |
| 100ml face serum | 45 |
| 200ml body lotion | 30 |
| 5kg dog food | 14 |
| Flea treatment (monthly) | 28 |
Adjust based on your actual repurchase data after 30 days.
The case for a dedicated reorder layer
General-purpose email platforms like Klaviyo can approximate reorder reminders with date-based flows. The configuration is complex, requires custom properties per product, and is difficult to maintain as the catalogue grows.
A dedicated reorder tool removes that friction. You configure usage days once per product. The reminder scheduling, send timing, and email copy are handled automatically.
Reorder Reminder Pro starts free — up to 30 reminder emails per month. No subscription required from customers. Works with any Shopify plan.
Also useful: generate direct checkout links to include in reminder emails — customers click and land directly at checkout with the product pre-added.