Formulas
Conversion rate = Conversions ÷ Visitors × 100%
Visitors needed = Target conversions ÷ Conversion rate
The "visitors needed" output assumes your conversion rate stays roughly constant as you scale traffic. In practice it tends to drop as you move from highly-targeted to broader audiences — model that drop-off when planning campaigns.
Worked example
A landing page received 5,000 visitors last month and produced 125 signups.
- Conversion rate = 125 ÷ 5,000 = 2.50%
- To hit 500 signups at the same rate, you'd need 500 ÷ 2.5% = 20,000 visitors
- That's 1 conversion per 40 visitors
FAQ
Should I count returning visitors?
Either is valid as long as you stay consistent. Unique visitors give a cleaner per-person rate; total sessions match what most ad platforms report. The trap is mixing the two month-to-month.
How big should an A/B test be?
For most landing-page tests targeting a relative lift of 10–20%, you'll need a few thousand visitors per variant before the result is statistically reliable. Small tests on small samples produce noise.