There is no calculator because its ever changing, it depends on how many coins you have in your wallet, how many other people have their wallet open with a lot of coins in the wallet to, it depends on the coins in your wallets age, it depends on the proof of stake difficulty also. So there is a lot of factors.
Ok! Thank you!
I have 3 weeks my wallet with 300k coin, no one coin rewards. I will not buy 20 mil of course

No need to have 20mil, but 300k too small for staking reward.