Here is a chart that you can use that will help.

I have updated it with Bitmains latest offering of the Antminer S9.


It seems that the network difficulty will be dropping. Perhaps due to BCH taking a little of the mining hardware out of the picture or older hardware being taken offline to to operating costs.

To clarify the chart I have is set to have an increase in difficulty at 1% every 18 days. THIS IS AN ESTIMATE. It may drop % a few times. However I have factored in the average increase over the last two years and even the average from the last year.

https://docs.google.com/spreadsheets/d/11QS1BBV11KNGTF8N_-fdfmjTZ3WzPQFbLfVrl5n6R8s/edit?usp=sharing




https://i.imgur.com/v4xu4s1.png - OLD DIFFICULTY from December 6th 2017

New from January 26 2018.
https://i.imgur.com/2oBJ4ZD.png