Glad to see so many have found this useful. I haven't even looked at it in months, I didn't' realize that it was so popular here.

Remember that this is an open sheet that any can fiddle with, so check all your Mining Factors in the grey box and make sure they fit your particular scenario. This means how many Mega Hashes your equipment is running, how many Watts you're using, the cost of electricity (if any) for you, how much you think the BTC will be worth when (and if) you sell them, ect...

Also if you want the most accurate difficulty forecast, enter the most recent ACTUAL difficulty and the date it started.

I suppose it depends on the rate of Bitcoins being destroyed. I can't imagine a shrinking number of coins in cirulation won't have any effect at all on their value.

The problem as I understand it is that there is a finite number of Bitcoins that will be mined, 21 Million. After that any coins that are hoarded and forgot about or destroyed by damaged media, are out of circulation, forever. This will lead to the number of BTC shinking over time.

It happens all the time with paper money and coins. They are destroyed, but the government replenishes the supply by printing more. What will happen to the value of Bitcoins once their is no printing more and the supply of them is diminishing?

I'm amazed how many people got dollar signs in their eyes and threw money at a company who produces vaporware, run by a known criminal. Personally I would never pay 100% of a products cost upfront for a preorder with no guarantee it will ever show up at my door. I might pay 10% to be put on a list and pay the rest when the unit is ready to be shipped.

My guess is that BFL is mining the crap out of all their machines right now and that they will ship them when the profitability is almost zero. Like other people on this forum have stated, why sell their money printing machines?

Which calcultations are you refering to? The sheet is open so people have been modifying all the input values. Or are you refering to some of the formulas that calculate the values on the left?

Sorry, I thought it was set so anyone could edit and plug in values to try, but apparently it was not. Now it's open so anyone can edit, feel free to adjust the values on the right...

https://docs.google.com/spreadsheet/ccc?key=0AmXn4BnLUgYsdEF0TUtWUWtUaUUzR1F2aUhEWW9lN2c#gid=0

That fixed point is the price of BTC when you sell them at some date in the future, ideally when it is highest. If you are worried about the price dropping you could sell your BTC as soon as you mine them, or periodically as you choose.

I don't want to get into that sort of speculation with this sheet, that's why I used a set amount. You can play still around with different BTC to USD conversion rates and see how the price will affect your net income.

Any thing based on speculation will get more and more innacurate the farther out you speculate. I think it's pretty close for the near term, but there are a lot of factors we can't predict right now.

As far as the difficulty rate increasing exponentially, I don't know how long it can continue. Maybe the growth rate will become more linear soon, even drop once the profitability goes down. If I had a crystal ball I'd be a millionaire. I guess that's why some people will AISCs are selling Meghash contracts, to curb the risk of the unknown for a set profit now.

It's not fixed. You can change the BTC price to whatever you want. It's just defaulted to the current price.

Yeah, the recent 28% difficulty  jump really makes the future of mining look bleak unless you have some serious hardware...

After reading about mining for a bit and pricing out some components on NewEgg I used a few of the calculators available on the web (such as http://www.bitcoinx.com/profit/). But all the ones I found were locked in at a certain difficulty level. This is not very useful for future projections when the rate of difficulty is increasing at an exponential rate. So, being a bit of an Excel junkie I created this spread sheet to see if GPU mining still has a chance to be profitable.

https://docs.google.com/spreadsheet/ccc?key=0AmXn4BnLUgYsdEF0TUtWUWtUaUUzR1F2aUhEWW9lN2c#gid=0

The outlook is not good for GPU miners. If my calculations are even semi accurate, there is no money to be made with GPUs, unless you own the hardware already and get free electricity. It seems GPU mining won't even pay for the hardware if you buy it now.

Please take a look at this sheet and share your thoughts on how fast you think mining difficulty will continue to rise in the future.

Has anyone actually gotten an Nvidia card to mine efficiently enough to pay for it's own power consumption? Or are these solely for people mining with "free" electricity?

ASCICMINER hardware costs WAYYY more per GH/s than BFL. That's why BFL smells like a scam. Because why would someone sell a device so profitable, for so little money?

I don't know about P2Pool, but on the bitcoipool.com FAQ, they have this to say...

Q: My hashing speed (mhash/sec) is different on the server and on my miner?

We view all the shares that were submitted in a 5 minute window (from 5 minutes ago to now), multiply by 2^32 (the size of a getwork) and then divide by the number of seconds in 5 minutes. Then divide by 1000 three times to make Gh/s. It's fairly accurate. Obviously you'll see inflated speeds if you submit more than one share per requested getwork, and the reverse is true as well. It's estimated. As there is no way for us to query the client itself, we have to guess, and this is the closest way to guess.

I've noticed that my hash speed on the pool is ussualy about half of what my cg or bfg miner says it is running at.

From what I've observed and read so far on these forums, it seems like BFL is a huge SCAM. I was intrigued by the claimed stats on their machines, but they haven't delivered anything except a few of the GH/s Jalepinos so far. They keep pushing deadlines back further and further.

In my experience if something sounds too good to be true, it probably is. Especially when it comes to investments. If a company manufacture these devices so cheaply why would they sell them? Others on this forum have speculated that BFL took preorder cash to design and build prototype AISC rigs, and then is going to use them to mine for themself.

At current mining rates these machines pay for themself in a month or two. Imagine how much BFL could make producing these things and then running them themself for a few months before shipping (if ever) to the customer...

Right now they are goign for over $1000 on ebay just for 300 MH/s. Not worth it at all, even if you pay high prices for elrctricity. It will take you 3 years to pay the thing off at current mining rates, which pretty much means you will never make your money back unless BTC prices go sky high.

At first when I noticed I could not reply to posts, I thought I missed a verification email or something. Then I found out about this 5 post + time limit thing.

It's kind of annoying, but I'm sure it cuts down on the spammers, trolls and noobs posting questions that have been answered 200 times already. So I guess if I have to troll the newb forum for a bit and do some research, then so be it.