CPM calculator
Cost per thousand impressions, in any direction.
Fill in the fields and the result will appear here automatically.
CPM states advertising spend per thousand impressions. The direct mode uses a reported spend and count; the inverse modes estimate a budget or impression count at a fixed rate. Repeated impressions can belong to the same person, so CPM is not the price of reaching a thousand unique people. Viewable impressions can also use a different reporting basis.
How it works
Formula and logic
For spend C, impressions I and CPM M: M = 1000C/I, C = M × I/1000 and I = 1000C/M. Cost per impression is M/1000. The inverse impression result is a mathematical estimate displayed to the nearest whole impression, not a delivery commitment. Actual input counts are not rounded. Ordinary money uses two decimal places and cost per impression four.
Example
45,000 monetary units for 1,200,000 impressions gives CPM 37.50 and cost per impression 0.0375. A budget of 30,000 at CPM 250 estimates 120,000 impressions; 1,000,000 impressions at CPM 37.50 require 37,500. Zero spend with 15,000 recorded impressions gives CPM 0.
Fields and units
- What to find — list option
- Campaign budget — $
- Impressions — unitless
- CPM — $
How to use
- — Select CPM, budget or impressions and enter only that mode’s two known inputs.
- — Reported impressions must be a positive whole count. Spend may be zero; a supplied CPM for an inverse calculation must be positive.
- — Before estimating delivery or budget, check whether a constant CPM is a reasonable assumption.
- — Use one currency and the same definition of an impression. No currency conversion takes place.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- Google Ads: a thousand impressions and the separate viewable-CPM basis
- Limitation
- Observed average or fixed-CPM estimate. Unique reach, viewability, clicks, sales and auction delivery are not forecast.
FAQ
Which denominator separates CPM from CPC?
CPM uses a thousand impressions, while CPC uses clicks. Cheap impressions do not establish cheap clicks or sales; review the campaign’s other outcomes too.
Does the inverse result guarantee an impression delivery?
No. It rearranges a constant-rate equation. Auction prices, available audience and serving constraints can make actual delivery different.
Can free placement have a CPM of zero?
Yes, with zero spend and a positive recorded impression count. Solving for impressions using CPM 0 would require division by zero and is rejected.
Can reach or viewable impressions replace ordinary impressions?
Reach describes unique audience members, whereas impressions can repeat. Viewable CPM uses a separate viewability basis. Comparing these as one metric requires an explicit adjustment and definition.