Runs created =
[(H + BB + HBP - CS - GIDP) times (Total bases + .26[BB - IBB + HBP] + .52[SH + SF + SB])] divided by (AB + BB + HBP + SH+ SF)

ESPN has already saved you the trouble of calculating them.

Arguably more useful, although generally similar results is Baseball Prospectus' stat, Equivalent Runs, or EQR. Not sure how to calculate, it's very complicated.
And RARP derives from EQR. I like RARP the best as a starting point for MVP debates. It calculates how many Equivalent Runs more than a replacement-level player at your position you've produced.