Two things on this site are for doing sums and looking words up, not for reading top to bottom. Both are free, need no account and collect nothing about you.
What is here
Wagering calculator
Enter the bonus amount, the wagering multiple, the game's RTP and its weighting. The calculator returns the total you would have to stake, the average cost of that play and what the bonus is worth after it.
Casino glossary
Plain definitions of the jargon in casino terms and conditions, from closed loop and KYC to la partage and must-drop jackpots, with the British rule attached where one exists.
If you want the reasoning behind the numbers, start with wagering requirements explained or browse all of our guides.