CPM, CPC & CPA calculator
One set of campaign numbers in, every cost metric out — CPM, CPC, CPA, CTR, conversion rate, ROAS, and the break-even ROAS your margin actually requires.
Campaign numbers
CPM — cost per 1,000 impressions
$5.95
- CPC
- $0.46
- CPA
- $15.43
- CTR
- 1.29%
- Conv. rate
- 3.00%
- ROAS
- 3.92×
- Break-even ROASThe ROAS you must clear to stop losing money at this margin.The ROAS you must clear to stop losing money at this margin.
- 1.82×
Profitable — 3.92× against a 1.82× break-even
Gross profit after ad spend is $2,890. With headroom this size, scaling spend is usually the right move before optimising creative further.
Break-even ROAS is 1 ÷ gross margin. A campaign at 3× ROAS is losing money at a 25% margin and printing it at 80% — the ROAS number alone tells you nothing without the margin.
How do you calculate CPM?
Divide total ad spend by impressions and multiply by 1,000. $2,500 spent for 420,000 impressions is a CPM of $5.95.
CPM on its own is a diagnostic, not a goal. Broadening your targeting will nearly always lower it, and will often raise your cost per acquisition at the same time — because you are paying less to reach people who convert less.
The four cost metrics
CPM = Spend ÷ Impressions × 1,000 CPC = Spend ÷ Clicks CPA = Spend ÷ Conversions Break-even ROAS = 1 ÷ Gross margin
What each metric tells you when it moves
The four cost metrics measure the same spend at four points in the funnel, which is what makes them diagnostic when you read them together:
- CPM high, CTR fine. Auction pressure or a narrow audience. The creative is working; you are just paying a lot to show it.
- CPM fine, CTR low. A creative problem. You are reaching people at a reasonable price and they are not interested.
- CTR high, conversion rate low. The ad is writing a cheque the landing page cannot cash. This is the most common and most fixable pattern.
- Everything fine, ROAS still poor. Your order value or margin cannot support the traffic cost. No amount of campaign optimisation fixes a unit-economics problem.
Why ROAS without margin is a meaningless number
ROAS gets quoted like a grade — 4× good, 2× bad. It is neither until you know the margin behind it.
A software business at an 85% gross margin breaks even at 1.18× ROAS. Everything above that is close to pure contribution. A retailer reselling at a 20% margin needs 5× just to stand still, and a 4× campaign that looks healthy on the dashboard is quietly destroying money on every order.
Set the margin slider to your real number and read the break-even figure first. It changes which campaigns you scale and which you switch off, and it is the single most useful output on this page.
From measurement to a media plan
This calculator works backwards from a campaign that already ran. To work forwards — turning a budget into projected reach, clicks and conversions, or solving for the spend needed to hit a revenue target — use the ad budget calculator. Feed it the CPM, CTR and conversion rate you just measured here and the projection will be grounded in your own data rather than an industry average.
Common questions
How do you calculate CPM?
Divide your total ad spend by impressions, then multiply by 1,000. Spending $2,500 for 420,000 impressions gives a CPM of $5.95 — that is what you paid for every thousand times the ad was shown.
What is the difference between CPM, CPC and CPA?
CPM is cost per thousand impressions, CPC is cost per click, and CPA is cost per acquisition or action. They measure the same spend at three points in the funnel. A low CPM with a high CPA means you are reaching people cheaply but they are not the right people.
What is a good CPM?
It varies enormously by platform, audience and season. Broad awareness campaigns often run in low single-digit dollars; narrow B2B targeting on LinkedIn can be several times higher. CPM also rises sharply in Q4 as advertisers compete for the same inventory. Your own past campaigns on the same platform are a far better benchmark than any published average.
What is break-even ROAS?
It is 1 divided by your gross margin. At a 50% margin you need 2× ROAS to break even; at 25% you need 4×. This is why ROAS alone tells you nothing — a 3× campaign is profitable at an 80% margin and losing money at a 25% one.
Should I optimise for a lower CPM?
Usually not on its own. Broadening your audience will reliably lower CPM and often raise CPA, because you are paying less to reach people who convert less. Optimise the metric closest to the outcome you actually want — normally CPA or ROAS — and treat CPM as a diagnostic.
Why did my CPM go up without changing anything?
Auction pressure. CPMs rise when more advertisers bid for the same audience — reliably around Black Friday and the December holidays, and whenever a competitor enters your niche. Audience fatigue does it too: as frequency climbs, platforms charge more to keep showing the same ad to the same people.
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