How to calculate the earnings?

How to calculate the earnings?
Before I start explaining about the calculation, I would like to introduce you to few terminology involved in Google Ad sense.

Page Impressions:

Page Impressions, in simple words! This is the number of times your page had been viewed by the people. This is the actual meaning! But to tell in terms of Google, This is number of times your webpage’s containing “Google Ad sense code”, has been viewed by the people.
For example: Imagine your website has 70 pages in it, and in each page you have added about 1 Google ad sense code. Now if your website has been viewed by 10 people per day, with average of 10 page views (page views are the number of pages each visitor views among your 70 pages). Then your Total page impressions will be 10x10x1 = 100 per day (as you have one Google Ad sense code per page).
So, every time your page has been visited, your page impressions increase which in turn increases the chance of your page getting clicked. More the clicks, more the revenue.

Once again Page Impressions is the number of times your Google AdSense code has been displayed on your webpage.

Clicks:

Clicks are the number of times your Google ads are being clicked upon. The more clicks you get more the revenue you get out of your website.

CTR: Click Through Rate:

“Click Through Rate” is the ratio between the number of clicks your ads get among the total Page Impressions. This will be your site’s CTR, this expressed in terms of percentage.
In simple words it’s the percentage of clicks your ads will get among the total page views
For example: Your average page view is 100 as per the above example and your clicks, imagining it’s about 10 per day. Your CTR is 10÷100x100 = 10% per day.

Page eCPM:

This is the Terminology to express the effectiveness of your website. In simple words this is the “Cost Per Thousand Impressions” you get from your website.
For example: Imagine if you have more than one website, then it will be easier to compare the revenue like – the money you get from 1st is $100 and the 2nd is $85. So, this is the way of expressing the money earned from thousand impressions on your website that’s all.

Now! Let’s talk business…
Actually Google doesn’t mention any where about the percentage of revenue they are sharing with you, though you can calculate your cost per click of your add
For example: you have earned $5 per day, w.r.t the above example.
The cost per click is “Money earned ÷ Number of clicks” that is $5÷10 = $0.5

All the above terms will be displayed in your Google AdSense account, and the example what I gave is all calculated for per day just multiply it by 30 for conversion to month.