Child turning 18 when does child support stop

I have three kids my oldest turns 18 this week. Does child support automatically stop for her after she graduates? Can I cut 1/3 of the child support off after she graduates or what do I need to do? Will it be recalculated for the other two after or just pay 2/3 of what I was paying?

Thanks Lost

No, you may not stop paying child support automatically, and it will likely not be reduced by one third. You must file a motion to terminate support for your eldest, and the court will recalculate the support based on there being two minor children. To get an idea of what the new amount will be you may want to check out the child support calculator on this website.