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CPM, CPC and CTR Calculator

All three delivery metrics from the three raw counts, plus the identity that ties them together.

✓ Recalculates as you type✓ The formula is printed on the page✓ Your figures never leave the tab

Delivery figures

Take all three from the same report and the same date range.

ImpressionsClicksSpend currency

Method

The arithmetic

Each metric is one division against a different denominator: click-through rate is clicks over impressions, cost per click is spend over clicks, and cost per thousand impressions is spend over impressions scaled by a thousand. Because all three are built from the same two counts and one cost, they are not independent — fix any two and the third is already decided.

CTR% = clicks ÷ impressions × 100 · CPC = spend ÷ clicks · CPM = spend ÷ impressions × 1000
identity: CPC = CPM ÷ (CTR% × 10)

Worked example

One run through the numbers

200,000 impressions and 3,000 clicks on 4,500 of spend is a click-through rate of 1.5%, a cost per click of 1.50, and a CPM of 22.50. The identity checks out: 22.50 divided by 1.5 times ten is 1.50, the same cost per click arrived at from the other direction.

Swap in your own figures — the result recalculates as you type.

Before you act on this

Where this number misleads

The identity is the useful part. It means a CPM buy and a CPC buy are the same buy priced differently, and that improving click-through rate lowers cost per click by exactly the same proportion at a fixed CPM. The CPM to CPC chart is that identity laid out in full.
Impressions are counted differently by different platforms — served, viewable, or viewed for a minimum duration — and CPM moves with the definition rather than with the media. Two CPMs from two platforms are not directly comparable without knowing which count each is using.
A rising CPM with a flat cost per click means the click-through rate improved. A rising cost per click with a flat CPM means it fell. Reading the two together tells you whether an efficiency change came from the creative or from the auction.
None of these three says anything about whether the traffic was worth buying. That question needs a conversion rate and an order value, which is what the ad budget calculator adds on top of these figures.
Click-through rate is bounded by the format, the placement, and the audience, so comparing one across placements measures the placement rather than the creative. Compare it against the same placement's earlier figure instead.

Asked often

CPM, CPC and CTR Calculator: questions that come up

What does CPM stand for?

Cost per mille — cost per thousand impressions, from the Latin for thousand. It is quoted per thousand rather than per impression because the per-impression figure would be an inconveniently long decimal.

How do I convert CPM to CPC?

Divide the CPM by the click-through rate expressed as a percentage times ten. A CPM of 20 at a 2% click-through rate is a cost per click of 1.00. The chart on this site tabulates the conversion across a range of both.

Is a lower CPM always better?

Not by itself. A cheaper thousand impressions shown to people who never click is more expensive per click than an expensive thousand that does. The identity above is the reason the two have to be read together rather than optimised separately.

Why does my platform report a different CTR than this?

Almost always a denominator difference. Some reports divide by served impressions and some by viewable ones, and some count all clicks while others count only clicks through to the destination. Both figures can be right about different questions.

Carry on

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