Firstly the calculators the above users are talking about are misleadingly called calculators. One expects a calculator to be very accurate but this cannot be because it cannot predict when miners shut down and begin because thst is s human action. Therefore predicting accurately is very difficult. But it does give you an idea of what to expect. If you time rentals well you can profit. Most people probably dont though. Like the above users spoke about its like giving free money away.
You see not everyone wants to monitor pools and the amount you csn mine st that time all day long so they just rent their rig out and let whoever rents it deal with that. Yes they lose money but its ok because that's not their field of expertise. It does make sense if you think about it. Its like if I sell you an apple nd you make a profit off it selling it at the market I dont care because I'm selling you 100 apples at a time and I can make more money faster that way. Also I am not good st selling apples but the guy I sell to is. So can you see ? The faster thinbgw move from hand to hand the more money to make.
I would just like to add that all the above users have bakid points so take it into consideration.
Mining "calculators" are based on the assumption that there is zero growth. I'll let you do the research on how that's a ridiculous assumption based on both past, present, and near-future. By nature of you even ADDING hash power, you've already started diluting your "calculated" earnings:
Hash power is 100 GH/s and a block pays 10 BTC
100 GH/s is calculated to be worth 10 BTC per block
You add 100 GH/s
You're NOT getting 10 BTC per block because you only account for 100/200 GH/s. You get half of what you "calculated"
Math doesn't lie.