Originally Posted by

**luckyc1423** have a simple math question.

If you have looking at a drilling rig. and you are trying to calculate downhole but rpm (revolutions per minute). and you have a motor right above the bit.

So your surface rpm say is 20 and your motor rpm say is 30....what would your bit rpm be?

is it just a straight addition? 20+30 = 50

for some reason I am thinking that if you have a surface rmp of 2 and a motor rmp of 30 you are spinning the motor twice...so when its still it rotats at 30 rpm but if you are spinning it twice wouldnt that be 62?