Ad and marketing maths, with the working shown
Eleven free calculators for the numbers media buyers, marketers and small business owners check every week. Each one solves for whichever figure is missing, writes the formula out with your own numbers, and keeps everything you type in your browser.
Buying attention
Winning customers
Judging the return
Planning and social
How the numbers are worked out
Every metric on this site is a definition, not an estimate: CPM is cost per 1,000 impressions, ROAS is revenue over ad spend, and so on. So the calculators can be exact, and they are tested that way. Each calculation runs on fractions rather than floating-point decimals, so $10 split three ways gives $3.33 every time, and a 2.625% conversion rate rounds to 2.63% the way you would round it by hand.
Before each release the calculators are checked against the worked examples published by Google Ads, Amazon Ads and Shopify, against hand-worked cases for every solve-for direction, and against a second, separate implementation run over hundreds of random inputs. The about page lists the sources and the checks.
What the site leaves out on purpose: industry "benchmarks". Typical CTRs, CPMs and engagement rates differ so much by platform, country, audience and year that a generic figure tends to mislead. Your own past campaigns are a better yardstick.
Questions
Which calculator should I start with?
Follow the money. If you buy impressions, start with the CPM calculator; if you pay per click, the CPC calculator. To judge results, use ROAS next to break-even ROAS. To plan spend, use the ad budget calculator.
Do the calculators convert currencies?
No. The currency menu only changes the symbol shown next to amounts. Enter every amount in the same currency and the maths is the same in any of them.
Is my data stored anywhere?
No. The calculations run in your browser and nothing you type is sent to us. The only thing remembered on your device is the currency symbol you picked.
Why does a result sometimes show four decimals?
When a money amount is not zero but would round to 0.00, such as the cost of a single impression, the calculator shows four decimal places so the figure is still visible.
Guides
- CPM, CPC and CPA: one campaign, three prices
CPM, CPC and CPA explained with one campaign worked from start to finish, the formulas that convert between them, and how to compare offers fairly.
- ROAS, ROI and break-even ROAS: which number answers which question
ROAS, ROI and break-even ROAS answer different questions. One campaign worked through all three shows when a good-looking ROAS is losing money.
- LTV:CAC: working out the ratio honestly
How to calculate the LTV:CAC ratio and CAC payback step by step, with a subscription and a repeat-purchase example, and the four inputs that inflate it.