In the US, child support is usually taken as a percentage of income from the "non" custodial parent, regardless of time spent living under care of that parent. This is an archaic way of handling this issue. It creates burdens that are not equally shared.
Australia has a system that requires BOTH parents to both nurture AND provide for the children. They determine the parental incomes & time spent in each home, and use a formula to determine the real world costs/expenses to the children.
This tool gives estimates.