PLAIN-LANGUAGE DEFINITION
CPM
CPM is spend divided by impressions, multiplied by 1000.
IN PRACTICE
An example
Spend of 500 across 50000 impressions gives a CPM of 10 in the chosen currency.
What this does not tell you
CPM is undefined when impressions are zero and does not measure sales performance.
Use the term precisely
When you use this term in a brief or report, include the relevant source, scope and assumptions. An example explains the concept; it is not a benchmark or a promise of results.