Calculating child support

I know the subject line is a pretty common question however, I’m trying to figure out what I should pay my ex-wife for one child. My oldest child (17yo) will be moving in with us in Oklahoma at the end of this school year. His mom will be moving to OK later this summer. My youngest son will be living with her.

What is the easiest way to calculate this? I’m fairly confident my youngest son will be spending the night with us quite often (we figure about 140 nights a year). My biggest confusion is, when calculating the updated child support for one child and the second child lives with another parent, should I include the court ordered amount that I’m to provide my oldest based on my current decree (in this case, $315 per child)?

Basically, my oldest will live with me and my youngest will live w/his mom.

I probably didn’t explain that to well so I apologize but I hope I explained it well enough that someone can make sense of it.

There is a child support calculator on this site at :rosen_dot_com/childcalculator/. In one of the steps there is room to put down payments made for child support to another mother.

No, you do not include the amount paid for your first child. My understanding of your facts below is that both of these children have the same mother.

Only if you have two children with different mothers would you include the amount you pay for one of the children.