How to Calculate Reorder Timing for Ecommerce Customers
You already have the raw material for reorder timing in your order history.
The simplest method:
- Identify customers who purchased the same product more than once.
- Calculate days between those purchases.
- Find the median.
- Examine the distribution.
- Adjust for quantity.
Example
Same-product reorder gaps:
28
30
31
33
34
91.
Median:
32 days.
Average:
The median better describes most buyers.
Use percentiles
Suppose:
25th percentile:
27 days
Median:
32
75th percentile:
Now you can build:
Early reminder
Day 27.
Main reminder
Day 32.
Late reminder
Day 40.
That is much stronger than one arbitrary date.
Recent replenishment guidance uses exactly this kind of percentile logic. (affinsy.com)
Adjust for units purchased
Expected reorder timing:
median per-unit consumption × quantity
Then validate against actual customer behaviour.
Frequently asked questions
Should I use average or median reorder time?
Usually both, but median is often less distorted by outliers.
Can reorder timing vary by customer?
Yes. Repeat customers with enough history can support individualized timing.
The principle
The order file is already telling you when customers tend to need more.
Listen to it.