The short answer
Cost per person lifted is media spend divided by persons lifted, where persons lifted is the absolute lift multiplied by the campaign’s reach. For example, a 9.7-point lift on a reach of 2.35 million is about 227,000 persons lifted; at £420,000 of media that is about £1.85 per person lifted.
Key takeaways
- Persons lifted = absolute lift (as a proportion) × reach.
- Cost per person lifted = media spend ÷ persons lifted.
- Carry the 95% range through, so the cost has a range too.
- Compare campaigns, placements and creatives on cost per person lifted, not on lift alone.
The steps
- 1
Take the absolute lift
Use the full-sample absolute lift on the primary KPI, as a proportion. A lift of +9.7 points is 0.097.
- 2
Get the campaign reach
Take the number of people reached from the media plan or delivery reports, not the number of impressions.
- 3
Calculate persons lifted
Multiply the lift by the reach: 0.097 × 2,350,000 ≈ 227,000 persons lifted.
- 4
Calculate cost per person lifted
Divide media spend by persons lifted: £420,000 ÷ 227,000 ≈ £1.85.
- 5
Carry the range through
Repeat the sums with the bottom and top of the 95% range. A range of +2.2 to +17.1 points gives roughly 51,000 to 403,000 persons lifted, and £1.04 to £8.16 per person lifted.
- 6
Compare like with like
Compare cost per person lifted across placements, creatives or campaigns that used the same KPI and audience definition.
The formulas.
Persons lifted = absolute lift × reach
Cost per person lifted = media spend ÷ persons lifted
A worked example.
| Input or result | Value |
|---|---|
| Primary KPI | Consideration |
| Absolute lift | +9.7 points (95% range +2.2 to +17.1) |
| Campaign reach | 2,350,000 people |
| Media spend | £420,000 |
| Persons lifted | about 227,000 (range about 51,000 to 403,000) |
| Cost per person lifted | about £1.85 (range £1.04 to £8.16) |
Why it beats lift alone.
A big lift on a small reach can change fewer minds than a modest lift on a large one. Google’s Display & Video 360 documentation makes the same point and recommends cost per lifted user as a primary success metric because it factors in both reach and cost. It also notes that lifted users are not necessarily unique people, so treat the figure as an estimate.
Common mistakes.
- Using relative lift instead of absolute lift, which inflates persons lifted.
- Using impressions instead of reach.
- Quoting the point estimate without the range.
- Comparing campaigns measured on different KPIs or audiences.
Questions
Is cost per person lifted the same as cost per lifted user?
They describe the same idea. Google calls it cost per lifted user; SpinProof calls it cost per person lifted. Both divide cost by the estimated number of people whose answer changed.
What if the lift isn’t significant?
If the 95% range crosses zero, the bottom of the persons-lifted range is zero or below, so the cost per person lifted has no upper limit. Report the result as no measurable change rather than quoting a cost.