Conversion Rate Calculator

What a conversion rate tells you

A conversion rate is the share of people who take a desired action out of everyone who had the chance to. The action, called the key event or goal, might be a purchase, a newsletter sign-up, a form submission, a download or a click on an advertisement. The group is whoever could have done it: site visitors, people who added an item to the basket, or users who saw an ad.

Because it is a ratio, the rate lets you compare pages, campaigns and time periods of different sizes on one scale. A page with 40,000 visitors and one with 4,000 can be judged side by side by the share who converted.

The formula

conversion rate = events ÷ usersAs a ratio, between 0 and 1 in the usual case.

conversion rate (%) = events ÷ users × 100

The calculator shows both forms. Percentages are rounded to four decimal places and the ratio likewise; when a result is a whole number or has no more than two decimals, it appears in the shorter form, so 10% pairs with a ratio of 0.10.

Fill in two boxes. Users is the number of people (or sessions, or impressions) in the group, and must be a whole number of at least 10. Events is how many of them converted, a whole number of at least 1. Decimal numbers are rejected because people and events are counted in ones. Events may exceed users, for example when one user can buy several times; the rate then passes 100%.

Worked examples

Online store. A shop has 2,500 visitors in a week and 75 of them place an order. The conversion rate is 75 ÷ 2,500 = 0.03, or 3%.

Basket to purchase. Of 400 shoppers who added something to their basket, 120 completed the purchase: 120 ÷ 400 = 0.30, or 30%. The remaining 70% abandoned the basket, which is where checkout improvements pay off most. Using the basket as the starting group rather than all visitors gives a number that isolates the checkout.

Advertising. An ad is shown 18,400 times and clicked 460 times. Treating impressions as users and clicks as events gives 460 ÷ 18,400 × 100 = 2.5%, the click-through rate.

Lead generation. A landing page gets 950 visits and 38 form submissions: 38 ÷ 950 = 0.04, so 4%.

Comparing rates over time

When a rate moves from 2.5% to 3.0%, two statements are both true: it rose by 0.5 percentage points, and it rose by 20% in relative terms (0.5 ÷ 2.5). Say which one you mean, because they sound very different. The percent increase calculator handles the relative change.

Always weigh the size of the sample. With few observations, chance alone moves the rate a lot. A rough 95% margin of error for a rate p measured on n users is 1.96 × √(p × (1 − p) ÷ n). For the store above, p = 0.03 and n = 2,500, which gives about ±0.67 percentage points, so the true rate plausibly lies between 2.3% and 3.7%. If only 3 of 40 visitors had converted, the rate would be 7.5% but the margin would be roughly ±8 points, too wide to decide anything.

A conversion rate says nothing about how valuable each conversion is. To judge whether the traffic pays for itself, combine it with revenue per conversion and cost, for example in the ROI calculator or the break-even calculator.

Common pitfalls

• Mixing the denominators. Rates measured on visitors, sessions and unique users are not comparable. Pick one and keep it.
• Averaging rates. To combine two periods, add the events and the users separately and divide, rather than averaging the two percentages.
• Mixing audiences. Traffic from search, email and paid ads often converts very differently, so a blended rate can hide a weak channel.
• Stopping tests early. A promising rate over a few days may not hold. Collect enough users before declaring a winner.