Quick answer
Conversion rate optimization (CRO) is the systematic practice of increasing the percentage of visitors or users who complete a desired action, such as a purchase or sign-up, by researching what prevents them and testing changes that remove those obstacles.
Formula: conversion rate = conversions ÷ visitors (or sessions) · value of a lift = visitors × (new rate − old rate) × value per conversion
What is conversion rate optimization?
Conversion rate optimization (CRO) is the practice of getting a larger share of visitors to complete a goal: buy, sign up, start a trial, request a demo. Instead of buying more traffic, you find out what stops the people already arriving and remove it.
The conversion rate is the starting point; CRO is the work of moving it.
The four-step CRO process
- Research. Find where people drop out with funnels and page reports, and why with heatmaps, session replay, surveys and usability tests.
- Hypothesis. "Because shipping costs appear only at the last step, people abandon checkout; showing them on the product page will raise completed orders."
- Test. Run an A/B test when traffic allows, sized in advance (statistical significance); otherwise ship and compare before and after carefully.
- Learn. Record the result, including failures, and feed it back into research.
What a lift is worth
A sample store with 50,000 visitors a month, a 2.0% conversion rate and an $80 average order:
| Conversion rate | Orders | Revenue | |
|---|---|---|---|
| Today | 2.0% | 1,000 | $80,000 |
| +10% relative lift | 2.2% | 1,100 | $88,000 |
A 0.2-point change is worth $8,000 a month without one more visitor. That arithmetic is why CRO pays off, and also why the denominator matters: compare rates with the same definition of visitors or sessions.
Common mistakes
- Testing without research. Button colours rarely matter; fixing a confusing step does.
- Stopping tests early when the result looks good.
- Optimizing one step and hurting the next, for example a pushier landing page that brings lower-quality leads.
- Ignoring segments. A change that helps desktop can hurt mobile.
Go deeper with conversion funnel optimization, what is a good conversion rate and landing page conversion rate.
See also: CRO audit, AI conversion rate optimization, Call to action.
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