Conversion Rate Optimisation
Conversion rate optimisation (CRO) is the practice of increasing the percentage of website or app visitors who take a desired action, such as buying, enquiring or signing up, through research, fixes and controlled testing.
How it works
CRO starts with research: analytics, session recordings, surveys and user testing show where people drop out and why. Clear problems get fixed. Uncertain ideas get A/B tested, with enough traffic and time to trust the result.
Public examples
- A single headline test at Bing lifted revenue by 12%, worth more than $100 million a year in the US (Harvard Business Review, 2017)
- Booking.com runs around 25,000 tests a year (Harvard Business Review, 2020)
- Baymard Institute estimates better checkout design could lift ecommerce conversion by around 35% (Baymard Institute)
- The median landing page converts at about 6.6%, based on 41,000 pages analysed by Unbounce (Unbounce, Q4 2024 data)
Formula
Conversion rate = (conversions / visitors) x 100
FAQ
How much traffic do we need for CRO?
For reliable A/B tests, usually a few thousand visitors a month to the pages being tested.
Is CRO just A/B testing?
No. Research and fixing obvious problems often deliver more than testing alone.
Published Sep 24, 2026 · Last updated Sep 24, 2026