If you're running a Bitaxe, your percentage chance of winning a block is:

0.000000000000000000000000000000000000000000119426751592357%

Over a year, your chances increase to:
0.00000000000000000000000000000000000000627707006369428%

Your chances of winning the UK national lottery (assuming 20M tickets sold and you buy one):

0.000005%

Over a year, your chances increase to:
0.00026%