Typical high-end computer graphics card will give you a hashrate of a few hundreds of MH/s. Let's say 500 MH/s (that may even be optimistic if you are using a laptop graphics card with no specific optimization or tweaking). According to a online mining calculator this gives you a whooping 0.00000629 BTC per day. <back in 2014> Which means it would take about
435 years to mine a single bitcoin. And that computation is not even worth anything because it assumes that the difficulty will remain constant, which it won't.
*Quoted from someone else's calculations back in 2014, but still applicable today. ^smile^
Source :
https://www.quora.com/How-much-CPU-time-is-needed-to-mine-1-bitcoinhttps://en.bitcoin.it/wiki/Non-specialized_hardware_comparison 
