Should I use the average or the median?

The median is usually better. A few very long gaps - a customer who returned after a year - pull the average up and make your reminders too late for most people. The median reflects the typical customer.

How do I calculate it for customers with only one order?

You cannot, because there is no second order to measure from. Those customers are counted in repeat purchase rate instead. For them, use the typical first-to-second gap of other customers to decide when to send a follow-up.

How does time between purchases relate to purchase frequency?

They are two sides of the same habit. Shorter gaps between orders mean more orders per year, so purchase frequency rises. Time between purchases is more useful for timing messages; purchase frequency is more useful for lifetime value.

When should I consider a customer lost?

A practical rule is when they have gone well past their usual gap - for example, two or three times the median for what they buy. Pick a threshold, apply it consistently and review it as your product range changes.

What Is Time Between Purchases? Formula, Benchmarks and How to Track It

Time between purchases is the average (or median) number of days between consecutive orders from the same customer. It sets the timing for replenishment emails and win-back campaigns, and it defines what "lapsed" means for your store.

Time between purchases is the typical number of days between one order and the next from the same customer. It is the metric that tells you when to remind customers to come back - and when a quiet customer has really gone.

Many stores email on a fixed calendar. Customers do not buy on a calendar - they buy when they run out or need the next thing. This metric lets you match your timing to theirs.

What Is Time Between Purchases?

Time between purchases (also called the repurchase cycle or purchase latency) is the average or, better, the median number of days between consecutive orders from the same customer. It only applies to customers who have ordered at least twice, because a single order has no gap to measure.

It does two jobs. It sets the timing for replenishment and "time to reorder" messages, and it defines what "lapsed" means for your store. A customer who usually orders every 40 days and has not ordered in 100 is behaving very differently from one who orders twice a year.

🧒 Explained simply Mrs. Lee buys a bag of dog food from your corner shop about every four weeks. If you put her favourite brand at the front in week four, she is happy. If six weeks pass and she has not come in, something has changed - maybe she found another shop.

How to Calculate Time Between Purchases

Time Between Purchases = Median days between consecutive orders per customer

Take every customer with two or more orders. For each pair of consecutive orders, count the days between them. Then take the median of all those gaps.

Say a store has three repeat customers:

Customer A ordered on day 0, day 30 and day 62 - gaps of 30 and 32 days.
Customer B ordered on day 0 and day 45 - a gap of 45 days.
Customer C ordered on day 0, day 28 and day 200 - gaps of 28 and 172 days.

The five gaps, in order, are 28, 30, 32, 45 and 172. The median is 32 days. The average would be about 61 days, pulled up by one long gap - which is why the median is usually the better choice.

Points to settle before you rely on it:

Per category, not store-wide. A store selling both coffee beans and grinders has two very different cycles. Mixing them gives a number that fits neither.
First-to-second gap separately. The gap between the first and second order is often longer than later gaps. It is worth tracking on its own, because it decides when to send your second-order nudge.
Same-day orders. A customer placing a second order an hour later to add a forgotten item creates a gap of zero. Consider ignoring gaps under a day.
Customers who never returned. They are not in the calculation at all, so read this metric alongside repeat purchase rate.

Why Time Between Purchases Matters

It times your reminders. A reminder just before the usual gap ends feels useful; too early it is ignored, too late the customer has bought elsewhere.

It defines "at risk" for your store. Without a subscription, no one cancels. Time between purchases gives you a sensible threshold: a customer well past their usual gap is the one to win back.

What Is a Good Time Between Purchases?

There is no good number in general - it is entirely product-specific. The right reminder timing for coffee and for mattresses is very different, and a shorter gap is only "better" if the product is genuinely used up faster.

Calculate it per category, then watch the trend for each cohort. Are customers who joined this year reordering sooner or later than last year's? Are gaps stretching after a price change? Those comparisons are more useful than any outside figure.

How to Improve Time Between Purchases

1. Send replenishment reminders on the customer's cycle

Trigger a reminder shortly before the usual gap ends for whatever the customer last bought.

2. Use the first-to-second gap for onboarding

If most second orders happen within a few weeks, focus your post-purchase emails on that window. Product tips, reviews and a relevant next item work best before the gap closes.

3. Set a clear win-back trigger

Pick a point - for example, twice the usual gap - after which a customer is treated as lapsed. Send a personal win-back message then, rather than leaving them in the regular newsletter.

4. Remove friction from reordering

"Buy again" links, saved details and one-click reorder from the reminder email shorten the step between "I need more" and the order.

How to Track Time Between Purchases

Chartsy for Ecommerce connects to your BigCommerce store with read-only access and syncs orders, products and customers every hour. It keeps every customer’s full order history, so you can see the gap between their orders and break it down by product or category.

Because the calculation uses each customer's real order history, repeat customers and their order dates are already there. Monthly customer segments - Loyalists, Promising, At-Risk and Lost - show who has gone past their usual rhythm. You can also ask ChartsyAI for a chart or report:

"What is the median time between orders for coffee customers?"
"Show customers who placed a second order within 60 days of their first"
"Which repeat customers haven't ordered in twice their usual gap?"

Try Chartsy for Ecommerce free for 14 days →

What is Time Between Purchases?

Key takeaways