You're gonna want about 336 GH/s (unless difficulty increases sometime this week!). Hope this helps.
336 Gh at 0.04 bitcoin ( today price) = 13.5 bitcoin so pretty much you will make 1 bitcoin every week and should break even in 13 week ) maybe 20 week after the difficulty increase
how is this not a good investment
?? at long the price of bitcoin is $500 now and $500 in 20 week time ? in 20 week you should still have earnt 13 bitcoin even if the cex.io price is 0.00001 per ghash your still going to break even in 6 months
am i misssing some thing
You are being careless with the numbers. Let's assume that the difficulty continues to increase as it has by 20%. Here is are your results from mining with 336 GHS:
| Period | Revenue (BTC) | Total Time | Total Revenue (BTC) |
| 1 | 1.67 | 2 weeks | 1.67 |
| 2 | 1.38 | 4 weeks | 3.05 |
| 3 | 1.16 | 6 weeks | 4.21 |
| 4 | 0.96 | 8 weeks | 5.17 |
| 5 | 0.80 | 10 weeks | 5.97 |
| 6 | 0.67 | 12 weeks | 6.64 |
| 7 | 0.56 | 14 weeks | 7.20 |
| 8 | 0.47 | 16 weeks | 7.67 |
| 9 | 0.39 | 18 weeks | 8.06 |
| 10 | 0.32 | 20 weeks | 8.38 |
Things to note:
- You do not break even after 13 weeks, or after 20 weeks. In fact, you never break even.
- After 24 weeks, your revenue is only 1/10th of what it was when you started.
- 20% per difficulty period is probably too generous. You can expect periods of 30% - 40% over the next few months.
- The time is not actually correct since the difficulty actually changes every 12 days in this case, not every 14 days.
You will break even as the difficulty wont always increase - one day It will flat and not increase . When it get too high to mine and ppl stop mining then it will come down to power cost . Most investor look at ROI in years not months .
