A conversion rate is the number of completed target actions divided by the number of eligible opportunities for those actions, multiplied by 100. The target might be a purchase, qualified enquiry, registration, or activation. The result is meaningful only when the action, denominator, time period, and counting rule are stated.
What is the conversion-rate formula?
Use: conversion rate = conversions ÷ eligible opportunities × 100. The denominator depends on the question. An advertising report may use tracked ad interactions; a landing-page analysis might use eligible sessions or users; a sales pipeline may use qualified opportunities. Google Ads defines its conversion rate as conversions divided by ad interactions that can be tracked to a conversion in the same period.
Do not silently move between users, sessions, clicks, and form starts. One person can generate several sessions or interactions, and one interaction may produce more than one counted conversion. Google Ads notes that a rate can exceed 100% when multiple conversion actions are counted for an interaction. A clear metric specification prevents an apparent improvement caused only by a changed counting setting.
- Name the conversion action and when it is considered complete.
- Define who or what is eligible to convert.
- State whether you count once per person, once per interaction, or every completed action.
- Use a fixed reporting period and document the attribution rule where relevant.
How should you compare conversion rates?
Compare like with like. A page receiving branded search traffic may convert differently from the same page receiving broad display traffic because visitor intent differs. Device, geography, new-versus-returning status, and customer segment can also change the mix. Segment the result when there is a plausible business reason, while retaining enough observations to avoid overreacting to random movement.
Check data quality before explaining a change. Confirm that the target action fires once at the correct moment, the denominator is still collected, consent and tracking behavior have not changed unexpectedly, and internal or test activity is excluded. Then examine the customer experience and test a specific improvement. A higher rate is valuable only if the action still represents a useful outcome and the volume and economics remain healthy.
- Report the numerator and denominator beside the percentage.
- Separate major traffic sources or customer groups when their intent differs.
- Watch conversion volume and contribution, not the rate alone.
- Use an experiment or additional evidence before claiming causation.
What mistakes make a conversion rate misleading?
A business can raise its rate by excluding lower-intent visitors while generating fewer total customers. It can also make a form easier to submit but attract more unqualified enquiries. Comparing a seven-day period with a longer conversion cycle can undercount actions that occur later. Duplicate events, changing primary actions, and mixing purchases with low-value page events can distort the numerator. Define a primary business outcome and keep diagnostic micro-actions separate so the metric continues to support the decision it was designed for.
A fictional landing-page calculation
A landing page receives 2,000 eligible sessions in September and records 80 completed appointment requests. Its session conversion rate is 80 divided by 2,000, multiplied by 100: 4%. After a form change, the page receives 1,500 sessions and 75 requests, a rate of 5%. The percentage increased, but completed requests fell from 80 to 75. The team checks traffic sources and the number of qualified appointments before deciding that the change improved the business outcome. It reports both periods' counts, rates, and qualification result rather than treating the percentage alone as success.