How to use it
Tap the figure you want to find in the equation at the top of the calculator: eCPM, revenue or impressions. The two boxes you need then appear. Copy the numbers from your ad network report for one date range; commas between thousands are fine, and you can shorten big counts to 250k or 1.5m.
The currency menu only changes the symbol shown next to money figures. It does not convert between currencies, so enter every amount in the same currency your report uses.
The formula
The e stands for effective, and the M is the Roman numeral for 1,000. Google AdMob describes eCPM as an estimate of the revenue you receive for every thousand ad impressions. Three versions of the same relationship cover every direction:
eCPM = revenue ÷ impressions × 1,000
Revenue = eCPM × impressions ÷ 1,000
Impressions = revenue ÷ eCPM × 1,000
Worked examples
These figures are made up to show the arithmetic. They are not typical rates for any network, format or country.
A website's display ads. A blog's ad report shows $864 of revenue from 360,000 impressions in March. $864 ÷ 360,000 = $0.0024 per impression, and $0.0024 × 1,000 = $2.40 eCPM.
An app's revenue from its eCPM. A mobile game's report shows an eCPM of $1.80 on 2.5 million impressions. $1.80 × 2,500,000 ÷ 1,000 = $4,500.00 of revenue. Each impression earned $0.0018.
Impressions needed for a revenue goal. The same blog wants $1,000 a month and assumes its $2.40 eCPM holds. $1,000 ÷ $2.40 × 1,000 = 416,666.7, so it needs about 416,667 impressions. Impressions come in whole numbers, so the calculator rounds and shows you the exact figure underneath.
| Revenue | Impressions | eCPM |
|---|---|---|
| $864 | 360,000 | $2.40 |
| $4,500 | 2,500,000 | $1.80 |
| $1,000 | 416,667 | $2.40 |
eCPM vs CPM
The sum is the same, but the money flows the other way. CPM is the advertiser's cost per 1,000 impressions; eCPM, as publishers and app developers use it, is their earnings per 1,000 impressions. If you are buying ads, use the CPM calculator instead.
The two rarely match for the same impression. Ad networks and exchanges between the buyer and the seller are paid out of the advertiser's spend, and your eCPM blends every way the ads were sold. Google's help page on AdMob eCPM floors notes that eCPM includes a blend of CPC and CPM ads, so a click-paid ad still counts towards revenue per 1,000 impressions.
Mistakes that skew an eCPM
- Mixing date ranges. Revenue for the whole month with impressions from one week gives an eCPM about four times too high. Take both figures from the same report and the same dates.
- Requests, matched requests and impressions. Ad networks count ad requests, the requests that got an ad back, and the impressions actually shown. These are three different numbers. eCPM divides by impressions, so dividing by requests makes it look lower than it is.
- Gross versus net revenue. Some reports show what advertisers paid, others show what you are paid after the platform keeps its share. Use the same basis for every period, app or site you compare, and say which one you used.
- Forgetting the 1,000. Revenue ÷ impressions on its own is the revenue from one impression. If your answer looks 1,000 times too small, the multiplication is missing.
How this calculator handles your numbers
Every figure you type is turned into an exact fraction before any division, so the result does not pick up floating-point noise. Money is rounded to two decimals at the end, half away from zero, and an amount that would show as $0.00 is given to four decimals instead. Impression counts are rounded to the nearest whole number. Zero impressions or a zero eCPM, where a division would be meaningless, get a plain message instead of an answer.