Unfortunately, it's not that simple. You'll need to account for frequency of the current, air space around the busbar, whether the bar is insulated (and with what), are your bars laminated, and how high you're willing to allow the temperature to rise. (You may already know all that, but I'm including it for the benefit of other readers.)
Here's an in-depth tutorial, including approximate formulas:
Unfortunately, it's not that simple. You'll need to account for frequency of the current, air space around the busbar, whether the bar is insulated (and with what), are your bars laminated, and how high you're willing to allow the temperature to rise. (You may already know all that, but I'm including it for the benefit of other readers.)
Here's an in-depth tutorial, including approximate formulas:
