Conversion Lift Calculator
How Much Better, Not Just Whether It's Better
Running a test against a control group answers a yes-or-no question by itself: did the test group convert more? Conversion lift goes a step further and sizes the effect — expressing the improvement as a percentage change relative to the control, which is what makes results comparable across tests with completely different baseline conversion rates.
The Formula
Control Conversion Rate = (Control Conversions / Control Visitors) × 100
Conversion Lift = ((Test Rate − Control Rate) / Control Rate) × 100
Lift is relative, not absolute — a move from a 2% to a 3% conversion rate and a move from 20% to 30% both represent a 1-percentage-point gain, but very different lift percentages (50% and 50%, coincidentally equal here since both are exactly a 1.5x multiplier — in general relative lift depends on the ratio between the two rates, not the point gap).
Worked Examples
| Test Conversions/Visitors | Control Conversions/Visitors | Test Rate | Control Rate | Lift |
|---|---|---|---|---|
| 620 / 10,000 | 480 / 10,000 | 6.2% | 4.8% | 29.17% |
| 150 / 5,000 | 120 / 5,000 | 3.0% | 2.4% | 25.0% |
A positive lift means the test group outperformed control; a negative lift means it underperformed. This calculator reports the raw lift and does not by itself confirm statistical significance — pair it with the A/B Test Calculator for that check.
Where This Calculation Matters
- Landing page and creative testing — quantifying how much a new page design or ad creative improved conversion versus what was already running.
- Promotional impact measurement — comparing a promotional offer's conversion rate against a non-promotional control period or audience.
- Feature rollout evaluation — measuring the conversion effect of a new checkout flow or onboarding step before a full rollout.
How to Use This Calculator
- Enter Test Group Conversions and Test Group Visitors.
- Enter Control Group Conversions and Control Group Visitors.
- Select Calculate to get both conversion rates and the resulting lift.
Related Calculations
Before acting on a lift number, confirm it isn't just noise with the A/B Test Calculator, which adds a statistical significance check to the same kind of comparison.