Explain Units + and -

[syph3n]

Hey everyone,
I was wondering how to calculate total units. Say I put 2 units on a game that is -110, how do I calculate my total units on a win or loss, is there a formula? I assume If i put 2 units on the game and lose its -2 units, but for a win is it like +1.8 units or something like that? Is there a formula for different lines such as if it was -115? Is there a program to do this or formula I can use in an Excel spreadsheet? I'm just a little confused, so if anyone could clarify this, I would appreciate it.

Thanks
Nick