Bottom Line:
- Conversion rate is a ratio - it captures frequency, not value, and optimising for it alone erodes contribution margin
- Revenue Per Session (RPS) combines CR and AOV into one number that actually tracks revenue
- Brands running CRO without RPS as a guardrail regularly trade margin for volume without realising it
Your agency sent over a report. Conversion rate is up 1.2 points. You check revenue. It's flat.
CR and revenue are not the same thing. The optimisation playbook for one can actively undermine the other.
The ratio problem
Conversion rate is orders divided by sessions. It captures how often people buy. Not how much they spend.
Two brands with identical traffic and identical conversion rates generate completely different revenue if their AOVs differ:
- Brand A: 2% CR, €85 AOV → €1.70 revenue per session
- Brand B: 4% CR, €30 AOV → €1.20 revenue per session
Brand B converts twice as often. Brand A generates 42% more revenue per visitor. If your north star is CR, Brand B wins. If your north star is revenue, Brand A wins.
This spread is common among brands that have run aggressive discounting or simplified checkout at the cost of upsells.
Revenue Per Session
Revenue Per Session (RPS) = total revenue ÷ total sessions. It captures both dimensions in one number. AOV improvements that don't move CR still show up. CRO tactics that lift CR by eroding AOV show up as flat or declining RPS. The signal is cleaner.
The most common CRO moves trade value for volume. Pop-up discounts pull in lower-intent buyers at reduced margin. Bundle-busting removes the upsell. Stripping product pages cuts the information that justifies a higher price. All of these lift CR. None of them are good for your LTV:CAC.
What to do with RPS
Add RPS to weekly reporting alongside CR. Segment by traffic source, device, and landing page - the gaps are where your optimisation priorities live.
CR up, RPS flat or down: you're converting more buyers at lower value. Check whether discounts or checkout changes are eroding AOV before you scale.
RPS up, CR flat: something is moving on the value side - upsells, cross-sells, discovery. Those changes compound better than volume improvements at thin margin.
Both up together: that's worth scaling. Those are the CRO wins that improve revenue frequency and revenue depth at the same time.
The metric you optimise for determines the business you build. CR optimisation builds volume. RPS optimisation builds margin.
Want to see if this applies to your store?