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Media Buying

Cost Per Mille (CPM)

Cost to reach 1,000 impressions. The KPI creates a shared view of audiences, visits, messages, and marketing actions when its population, event rules, and reporting window are documented.

Business context

Why Cost Per Mille matters

Trend Cost Per Mille with its numerator, denominator, or contributing inputs so that a shift in scale is not mistaken for an efficiency change.

Business question
Where does Cost Per Mille differ most across comparable teams, products, channels, or periods?
Teams that use it
Marketing, growth, channel, content, and commercial analytics teams.
Decisions it supports
Channel investment, campaign optimisation, audience strategy, creative testing, and conversion improvement.
Calculation

Cost Per Mille formula

(Total Ad Spend ÷ Total Impressions) × 1,000

Formula components

Ad Spend
The monetary amount assigned to ad spend for the same scope and reporting period used by Cost Per Mille.
Impressions
The consistently counted impressions included in the metric’s documented population and period.
Reporting period
The consistent day, week, month, quarter, or year covered by every input.

How to calculate Cost Per Mille

  1. Define the business scope, reporting period, and the event or status that qualifies for Cost Per Mille.
  2. Remove duplicates and exclusions according to the documented rule, while retaining a reconciliation count.
  3. Collect each input in the workbook formula from systems that use the same cut-off and unit.
  4. Apply (Total Ad Spend ÷ Total Impressions) × 1,000 and label the result with its period, unit, and relevant segment.
Worked example

Cost Per Mille example

A fictional digital marketing team calculates Cost Per Mille for one agreed reporting period.

  1. Ad Spend = £9,600.
  2. Impressions = 800,000.
  3. Cost Per Mille = £9,600 ÷ 800,000 × 1,000 = 12.

Cost Per Mille is 12.

The scaled result can now be compared with like-for-like periods that use the same denominator.

How to interpret the result

Compare Cost Per Mille over a consistent cadence and break it down only by segments large enough to support a decision. Review the formula inputs beside the result so teams can distinguish a real operating shift from a denominator or mix effect.

There is no single target that fits every organisation. Interpretation depends on channel, audience, campaign objective, placement, geography, attribution rule, and measurement window. Document the comparison group before labelling a result strong or weak.

Common mistakes and limitations

Inconsistent scope
Changing the included business units, products, channels, or populations makes the trend look different even when underlying performance is unchanged.
Mismatched periods
Formula inputs from different cut-off dates or time windows do not describe one coherent result.
Mixing accounting treatments
Gross and net amounts, recognition dates, allocations, refunds, taxes, and capitalisation rules must be applied consistently.
Assuming one universal target
A useful comparison depends on channel, audience, campaign objective, placement, geography, attribution rule, and measurement window; use like-for-like internal trends and clearly documented peer groups.
Cost Per Click (CPC) Average cost of a single click. Cost Per Action (CPA) Cost of driving a specific action (purchase, signup, etc.). Cost Per Lead (CPL) Cost of generating a single lead. Paid Media Click-Through Rate (CTR) Percentage of impressions that led to clicks.

Turn metric definitions into answers your team can use.

Vizma helps teams understand and track business metrics using their data. Bring your Cost Per Mille definition, underlying data, and reporting questions to a Vizma demo.

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