currently difficulty is at 37. and is estimated to jump to 50. which is %40 increase so, if this trend continues, we are talking %120 increase per month or %240 per 2 month
that is why I decided not to buy knc Jupiter at the moment, even if it is delivered in October as promised I still would not make ROI.
here is a better calculator
http://mining.thegenesisblock.com/even if you assume difficulty will increase %35 per 10 days and round it off to %100 per month the outlook is bleak Why would you round that off to 100%? A rate increase of 35% every 10 days is a rate increase of 146% over a 30 day period. That would take a 50M difficulty up to 123M in one month and then on to over 300M in 60 days. (You need to multiply percentage increases not add them.)
If the network hash rate increases at the same rate as in the last cycle, that is where we will be in 60 days - a difficulty of 300M.
That begs an important question. Will hash rates keep rising at 35% per cycle? What can we see from the network today? We are currently one third of the way through the current cycle and allchains.info estimates a 17.7% increase for the next cycle. Of course, that is not a real estimate. It really means that, over the last 3 days, the net has added enough hashing power to require a 17.7% increase in difficulty. The are seven more days to go before the next recalculation and there will surely be more hash power by then. If the trend over the last three days continues then the next difficulty jump would be greater than the last one. Of course random variance has a role to play in this and things may not be as bad as that - but equally, they may be worse.