This free CPM calculator works out cost per thousand impressions and four related ad metrics: CPC, CTR, CPA and ROAS. Enter any two values on a tab and it solves for the third, which helps marketers plan budgets and judge campaigns.
- How to use the CPM calculator
- The five formulas the calculator uses
- How to calculate CPM, with an example
- How CPM, CTR and CPC connect
- What is a good ROAS? Break-even first
- Planning a budget with the calculator
- FAQ
- Related tools
How to use the CPM calculator
- Pick the tab for the metric you need: CPM, CPC, CTR, CPA or ROAS.
- Enter any two of the three values on that tab. For example, on the CPM tab enter cost and impressions to get CPM, or enter CPM and impressions to get the cost.
- Read the result, which updates as you type. Check that the units match: cost in one currency, impressions as raw numbers, not thousands.
- Switch tabs to follow the chain. A CPM tells you the price of reach, CTR tells you how many people respond, CPC and CPA turn that into cost per visit and per sale, and ROAS shows whether it paid back.
- Change one input to test a what-if, such as a lower CPM or a higher click-through rate, and compare the new result with your target.
All calculations run in your browser. Nothing you enter is sent anywhere, so you can use real campaign numbers.
The five formulas the calculator uses
Cost per thousand impressions. Total cost divided by impressions, multiplied by 1,000. The standard price unit for display, video and social ads.
Cost per click. Total cost divided by clicks. It shows what each visit to your page costs.
Click-through rate. Clicks divided by impressions, as a percentage. It measures how often people who saw the ad clicked.
Cost per acquisition. Total cost divided by conversions, so you can compare channels by what a sale or lead costs.
Return on ad spend. Revenue divided by cost. A ROAS of 4 means $4 of revenue for every $1 of ad spend.
How to calculate CPM, with an example
CPM stands for cost per mille, where mille means one thousand. The IAB and ad platforms use it as the common price unit for impressions. The formula is:
CPM = (Total cost / Impressions) x 1,000
Worked example: you spend $500 and your ad is shown 250,000 times. CPM = 500 / 250,000 x 1,000 = $2.00. You can also run it backwards. If a publisher sells at an $8 CPM and you want 100,000 impressions, the cost is 100,000 / 1,000 x 8 = $800.
Publishers use the same maths from the other side. A site with 400,000 monthly ad impressions at a $2 effective CPM earns 400 x 2 = $800 a month. In advertising, a lower CPM is not automatically better, because cheap reach can mean the wrong audience. Always read CPM next to CTR and CPA.
How CPM, CTR and CPC connect
The five metrics are linked. If you know CPM and CTR, you can find CPC without any click data:
CPC = CPM / (1,000 x CTR), with CTR as a decimal
Worked example: a $2 CPM and a 0.4% CTR (0.004). That gives 2 / (1,000 x 0.004) = $0.50 per click. Use the CTR tab to check the rate: 1,200 clicks on 80,000 impressions is 1,200 / 80,000 x 100 = 1.5%.
Then follow the money. If those $0.50 clicks convert at 2%, CPA = 0.50 / 0.02 = $25. Use the ROAS tab to see whether $25 per sale is profitable: 30 sales at $60 each is $1,800 of revenue, and with $750 of spend, ROAS = 1,800 / 750 = 2.4.
This is why a high CPM is not always a problem. A premium placement with a high CTR can still deliver a cheaper click than a cheap placement nobody notices.
What is a good ROAS? Break-even first
There is no universal good ROAS, because it depends on your margin. Start with break-even. If your profit margin on a sale is 25% before ad costs, you need revenue of 4 times your spend just to cover it:
Break-even ROAS = 1 / profit margin, so 1 / 0.25 = 4.0
Any ROAS above that makes money on the first sale. Below it, you only profit if customers come back, so factor in repeat purchases and lifetime value. A business with 60% margin breaks even at a ROAS of about 1.7. Always calculate your own number rather than copying a benchmark from another industry.
Common mistake: mixing platform-reported conversions with real sales. Ad platforms may count the same sale twice or claim a conversion that began elsewhere. Check ROAS and CPA against your own revenue data before you change budgets.
Planning a budget with the calculator
Work backwards from the goal. Say you need 50 sales and your target CPA is $25. The budget is 50 x 25 = $1,250. If the average CPC is $0.50, that buys 2,500 clicks, and at a 2% conversion rate those clicks give you 50 sales. If the numbers do not line up, change the input you can influence, such as the landing page or the creative.
A good CPM calculator also helps you spot where a campaign leaks. Low CTR points to weak creative or targeting. Good CTR but poor conversion points to the page. High CPA with good ROAS may simply mean a high-priced product. Test one change at a time and record the results, so you know what actually moved the numbers.
Frequently asked questions
How do you calculate CPM?
Divide total cost by impressions, then multiply by 1,000. For example, $500 spent over 250,000 impressions gives a CPM of $2.00. The calculator does this when you enter cost and impressions on the CPM tab, and it can also solve for cost or impressions if you know CPM.
What is a good CPM?
There is no single good CPM. It varies by channel, audience, country, format and season, so compare against your own past campaigns and your CPA. A cheap CPM that brings no conversions is worse than a higher one that produces sales at an acceptable cost.
What is the difference between CPM and CPC?
CPM is the price you pay for 1,000 impressions, regardless of clicks. CPC is the price you pay for each click. Under CPM buying you carry the risk of low engagement. Under CPC buying the platform carries more of it. You can convert between them using CTR.
How do I use this as a CTR calculator?
Open the CTR tab and enter clicks and impressions. It returns click-through rate as a percentage, using clicks divided by impressions times 100. You can also enter CTR and impressions to estimate clicks, which helps when forecasting traffic for a planned campaign.
How is ROAS different from ROI?
ROAS divides revenue by ad spend, so it ignores product costs and overheads. ROI looks at profit after all costs. A campaign can have a healthy-looking ROAS and still lose money if margins are thin, which is why you should compare ROAS with break-even.
Can I use this ROAS calculator for any currency?
Yes. Enter costs and revenue in the same currency and the result is a ratio with no unit. Just keep impressions and clicks as plain counts, not in thousands, so that CPM and CTR come out right. Nothing is saved or sent from your browser.