How do casino’s calculate thier odds on thier games?

For instance, if I am a casino, and I have a game that pays out $100,000 on a $1 bet, but you have a 1 in 120,000 chance of winning, it is obvious that the house is much better odds in the long run.

What I am wondering is how the house odds (or gamblers odds) are calculated in such an example. Is it 60% for the house for example?