What category penetration reveals about untapped spend
The short answer
Category penetration is the share of active customers who bought from a category in the past year. Calculate it for every category, then value the gap: the extra buyers needed to reach a target penetration, multiplied by what a typical buyer spends there. Large categories with low penetration among your best customers are the biggest untapped opportunity.
Cross-category opportunity, valued
Why it matters
Many customers buy from only a few of your categories, so each category they never try is spend going to a competitor. Valuing the gap tells you which cross-sell opportunities are worth campaign budget and which are too small to chase.
The question to ask
Copy this into Lexi as written.
How to work it out
1. Count buyers per category. For each category, count active customers who bought from it in the past year, across store and online.
2. Set a target. Use the penetration among your most active customers, or a related category, as a realistic target for each category.
3. Value the gap. Multiply the extra buyers needed to reach the target by average annual spend per category buyer, and check which customers are most likely to cross over.
What the answer looks like
Illustrative output on sample data
Illustrative example: how Lexi answers this for a home improvement retailer with 200,000 active customers. It measures the share of customers buying in each category.
- Paint: 42% penetration
- Garden: 23%
- Lighting: 9%
What the data shows
Lighting has the lowest category penetration, but among regular paint and tools customers it reaches 17%.
What it means
Raising lighting from 9% to 13% would add 8,000 buyers. At $140 average annual lighting spend, that is about $1.1 million a year.
What to do
Target recent paint customers working on interior projects with a lighting offer.
Would you like me to build that cross-sell segment for Klaviyo?
Frequently asked questions
How do I set a target for cross category penetration?
Use your own customers as the benchmark. Penetration among your most active customers, or among customers who already buy a closely related category, shows what is realistic. Aim for a share of that gap, since your whole base will not behave like your best customers.
Why not value a category gap at full penetration?
Not every customer needs every category. A customer who rents may never buy garden supplies, however good the offer. Valuing the gap at 100% inflates the opportunity and spreads budget thin. A target based on similar active customers gives a figure you can plan around.
Which customers should a category introduction target?
Customers whose recent purchases point to a need the category meets, such as a paint buyer starting a room project. Purchase history, the paths of similar customers and timing since their last order help rank them. Send the introduction while the related project is still underway.