CPM calculator
Fill in any two of spend, impressions and CPM — the third one is calculated.
Runs entirely in your browser. Nothing you paste is uploaded or stored.
Fill in any two — the third is calculated. Add clicks to get CTR and cost per click as well.
Leave exactly one of spend, impressions or CPM empty and it will be filled in.
What this tool does
It solves whichever of the three numbers you left empty: cost per thousand impressions, total impressions, or the budget needed to buy them. Add clicks and it also gives you click-through rate and cost per click, which is where a media plan usually starts to look different from the spreadsheet it was written in.
Reading the number
CPM prices attention, not results. It is the right metric for comparing placements, and the wrong one for judging a campaign — a placement can be half the price and still be more expensive per customer.
The relationship worth memorising is between CPM, CTR and CPC. At a fixed CPM, click cost is entirely a function of click-through rate: CPC = CPM ÷ 10 ÷ CTR%. A campaign with a €4 CPM and a 0.4% CTR is buying clicks at €1. Lift that CTR to 0.8% and the same inventory costs €0.50 a click — better creative, not a better deal from the platform.
Where CPM misleads. Two placements with identical CPM can differ tenfold in viewability. An impression that never enters the viewport is counted, billed, and worthless. If a supplier will not quote viewability alongside CPM, treat their number as a ceiling rather than a price.
Questions
What is the CPM formula?
CPM equals total spend divided by impressions, multiplied by one thousand. The multiplication is the whole point of the metric: display inventory is priced per thousand views because per-view prices would be fractions of a cent.
Why does the calculator solve in three directions?
Because the question changes depending on where you are. Planning a campaign you know the budget and the quoted CPM and want reach. Reporting on one you know spend and impressions and want the CPM. Negotiating you know the reach you want and the CPM you will accept, and need the budget.
Is a low CPM good?
Only if the impressions are worth having. Cheap inventory is cheap for a reason — a broad untargeted audience will always undercut a narrow one on CPM and lose on everything that follows. Judge CPM next to CTR and cost per acquisition, never alone.
How do CPM, CPC and CTR relate?
CPC equals CPM divided by ten, divided by CTR expressed as a percentage. That relationship is why a small CTR improvement moves cost per click so much: at a fixed CPM, doubling CTR halves your CPC.
Does this send my numbers anywhere?
No. Everything is calculated in your browser, and nothing is stored or transmitted.