What is CPM?

CPM (cost per mille) is what you pay for 1,000 impressions. It measures the cost of reach, regardless of clicks.

CPM = (Spend ÷ Impressions) × 1,000

Worked example: £225 ÷ 10,000 × 1,000 = £22.50.

Common beginner mistake: Leaving out the × 1,000, which gives the cost of a single impression.