Google converts advertisers’ payments from their currencies to your payment currency using the prevailing market rate from the day before the ads were shown. Google gets its rates from major banks, and other industry-recognised rate sources.
For example, let’s say that you get paid in euros, and an advertiser purchases ads on your site using US dollars on 15 August. Google will then calculate your earnings using the dollar to euro exchange rate from the end of 14 August.
Note that if your bank account is denominated in a different currency to your payment currency, when you get paid your bank may apply their own currency conversion (using their own exchange rate) or even reject your AdSense payment. In either case, you should contact your bank directly for more information.
The Exchange Rate For Reports
Google converts currencies in reports in the same way. This means that reports in your payment currency should reflect the amount that you’ll be paid.
Reports in a different currency reflect the amount that you’d be paid if you were paid in that currency.
When viewing reports in a different currency to your payment currency, the reported values (based on daily exchange rates) might not match your own calculations, if you’re exchanging your earnings into that currency using a later exchange rate.