What share of visitors do the thing
Conversion rate is the fraction of visitors who complete the action a page exists for — a purchase, a signup, a form. It is the single number that connects traffic to outcomes, and the one that decides whether more traffic is worth buying.
The formula
Worked example: 450 conversions from 15,000 visitors
- Conversion rate: 3.0%
Now attach money to it. At $60 average order value that is $27,000 of revenue. The interesting question is what a small improvement is worth:
| Rate | Conversions | Revenue at $60 | Gain |
|---|---|---|---|
| 3.0% | 450 | $27,000 | — |
| 3.5% | 525 | $31,500 | +$4,500 |
| 4.0% | 600 | $36,000 | +$9,000 |
Half a percentage point is worth $4,500 on the same traffic. Buying 2,500 more visitors to achieve the same result would cost real money; the rate improvement costs a change to the page.
Why the denominator decides the answer
The same shop can report 3%, 8% or 25% depending on what counts as a visitor:
- All sessions: 3.0%
- Sessions that reached a product page: perhaps 8%
- Sessions that started checkout: perhaps 25%
None is wrong; they answer different questions. Benchmarking your figure against an industry average is meaningless unless both use the same denominator, and published averages rarely say which they used.
When the number is not yet real
At 3%, a test needs roughly 1,000 conversions per variant before a 10% relative improvement is distinguishable from noise — around 33,000 visitors each side. Most tests are called long before that.
A jump from 3.0% to 3.4% on 500 visitors is not an improvement, it is fifteen conversions against seventeen.
What this calculator leaves out
Traffic quality. A rate that falls after a new campaign often means the campaign brought worse-matched visitors, not that the page got worse. Segment by source before drawing conclusions.
Conversion rate against value per visit
Optimising the rate alone can lose money. A discount banner that lifts conversion from 3.0% to 3.6% while cutting average order value from $60 to $48 produces $25,920 against $27,000 — more buyers, less revenue.
The figure that cannot be gamed this way is revenue per visitor: $27,000 ÷ 15,000 = $1.80. Track that alongside the rate, and any change that raises one while lowering the other becomes visible immediately.
Where to look when the rate is low
A 3% rate means 97 of every 100 visitors left without acting, and they did not all leave at the same place. Break the journey into steps and the leak becomes locatable: landing to product, product to cart, cart to checkout, checkout to paid.
Industry-wide, cart abandonment runs near 70%, and the two causes that dominate are unexpected shipping cost and a forced account creation. Both are visible in an exit rate report and both are fixable without touching the product page everyone assumes is the problem.
Related calculators
- Cost per acquisition — what each conversion costs to buy
- Bounce rate calculator — visitors who left immediately
- ROAS calculator — revenue against advertising spend