Wisconsin uses the standard percentage formula, set by DCF 150 of our State Legislature. The percentage is based on the number of kids to be in primary placement of a parent: For 1 child, it's 17% of gross income; For 2 children, it's 25% of gross income; For 3 children, it's 29% of gross income; For 4 children, it's 31% of gross income; For 5+ children, it's 34% of gross income.