YouTube money calculator
Estimate what a video or a channel earns from ads, based on views, niche and audience country. The figure it returns is an order of magnitude, not a forecast: what actually reaches your bank account is set by how many views carried an ad, invalid-traffic adjustments, tax withholding and currency conversion. Why the two numbers never match.
If your rate has fallen rather than your revenue, the question is a different one: why your RPM dropped.