http://www.bitcoinx.com/profit/ http://www.bitcoinx.com/profit/ is an example. Note that the initial values (60,000MHash/sec, and a very tidy profit in 3 month

http://www.bitcoinx.com/profit/ http://www.bitcoinx.com/profit/ is an example. Note that the initial values (60,000MHash/sec, and a very tidy profit in 3 months) are appropriate only for one of the specialised hardware options. If you start filling it in with realistic values for a PC with a graphics card (see, e.g., https://en.bitcoin.it/wiki/Mining_hardware_comparison https://en.bitcoin.it/wiki/Mining_hardware_comparison) you'll likely find the calculations running rather less in your favour. Profiting is also much easier when bitcoins are $188 each than it is when they are $10 each.