as with any gear ratio it is the number of teeth on the driven gear compared to the drive gear, on a planetary gear set it depends which gear you are using, as several are possible, depending on which member you hold and drive. In ratios all things are equal, so calculate the ratio and use the input torque, to calculate the output torque, same goes for the speed of the gears or shafts. For example on a 2 to 1 gear ratio, torque is doubled, and output speed is cut in half.

ttps://sciencing.com/calculate-planetary-gear-ratio-6002241.html