Thanks for your quick feedback!

Actually, I've got data from the 4th of December as well, here's compared to the 17th and the 18th (today):

04/12/2017: 4.41 btc/month
17/12/2017: 3.73 btc/month
18/12/2017: 3.17 btc/month

The trend is going downwards. Do you mean the calculator is wrong, or that there will be a correction and all of a sudden we'll go above 4 btc/month again with these 800TH/s?

The only predictor I have to measure the return on investment of my operation is the Antpool's calculator, which offers the same results as Cryptocompare's: https://www.cryptocompare.com/mining/calculator/

If these are wrong, then how can we evaluate the success of a potential mining enterprise?

Cheers