Is there any way to tell how much I would weigh on another planet?

You just need to know the strenght of gravity on that planet. On Earth it is 9.8 meters per second per second. On the Moon it is 1.7 meters per second per second. So your weight on the moon is roughly 1/6 what it is here on Earth.

So if you want to lose some weight, just go to the Moon! Unfortunately, since your mass is constant, any love handles or bulges you may have will go with you!