The percentage of RTP given to the players varies from casino to casino. But on average, the percentage is around 90% to 96% or more in some online casinos. Also, the percentage of RTP is fewer in offline or land-based casinos because of the maintenance and setup of physical slot machines. RTP is calculated by a simple formula, i.e. The total number of winnings divided by the total amount wagered for gambling. The calculation is performed by the computer algorithm of the online casino after thousands of bets.