What conversion rate measures
Conversion rate is the percentage of people who took the action you wanted out of everyone who had the chance. The formula is conversions divided by the eligible audience, times 100. If 2,000 people land on a product page and 50 buy, the page converts at 2.5 percent. The hard part is choosing the denominator: sessions, unique visitors, ad clicks and video viewers all give different answers for the same campaign.
Always state both halves when you quote one. "Click to purchase" on an ad is not "session to purchase" on the store, and an app's "install to trial" is a third figure again. Comparing a creator ad's click-to-purchase rate with last year's sitewide rate is a common way to fool yourself in a weekly report.
Where a creator video changes the number
Creator content touches conversion in two places. In the ad, a clear demonstration pre-qualifies the click, so fewer curious people and more ready buyers reach the page; the click-through rate may fall while purchases per click rise. On the page itself, a short testimonial video near the add-to-cart button answers the doubt a product photo cannot, such as how a fabric moves or how big a bottle really is.
That is why a video can look weak on clicks and strong on sales. Judge it on cost per acquisition, which multiplies both effects together, rather than on either rate alone.
Reading it without fooling yourself
Small samples swing wildly. Ten purchases from 300 clicks is 3.3 percent; one more sale makes it 3.7. Wait for at least a few dozen conversions per variant before you call a winner, and compare variants over the same days so a payday weekend does not decide the test.
Hold the landing page constant while you test creative, and the creative constant while you test the page. Change both at once and the rate moves, but the cause stays a mystery.
How it's used
The new demo video converts at 4.1 percent click to purchase against 2.8 for the static ad, on roughly the same spend.
Before we compare these, are we both using sessions as the denominator, or is your number per unique visitor?