Q: So I’m not understanding is child support determined by how much time the child spends with one parent?

A: Without an agreement, the courts calculate the child support amount according to a guidelines chart, based upon the combined gross monthly income of both parents. That gross income number determined the amount of money it takes per month for parents at that income level to raise the child(ren) (the more children, the greater the number). Then each parent is assigned their proportionate share of that number. The parent having primary physical custody does not pay their share to anyone, as they are deemed to be spending that amount already. The non-custodial parent (the one with visitation rights) pays their share to the primary custodial parent as child support. Added on top of that number is a share of child care expenses, extraordinary medical expenses of the child, etc. If the non-primary custodial parent has the child(ren) at least 128 OVERNIGHT vists or more per year (35% of the time or more), then custody is deemed "shared" and the amount of the child support obligation owed by the non-primary custodian goes down based on the number of excess overnight visits (there's a separate math calculation for that). So, you will see non-custodial parents often trying to guarantee at least 128 overnight visits per year to cut down on the child support, and the primary custodial parent trying to prevent that so as to maintain a higher support level. Of course, it is normally in the child's best interests to spend as much time with both parents as possible so long as everyone is getting along; however, in the absence of an agreement, judges rarely grant shared physical custody, so most custody and child support awards are for sole physical custody for one parent and with visitation rights to the other parent. If the parents can agree, then they can work out different arrangements. Primary vs. shared physical custody of children should not be confused with sole legal vs. shared legal custody. "Legal" custody controls who has authority to make major decisions regarding the care and upbringing of the child (health and medical decisions, schooling, religious upbringing, right to take the child out of the country and manage passports, etc.). One parent can have both sole legal and physical custody, or shared legal and sole physical custody, or any combination. The parties by agreement can even reserve to the non-sole legal custodian certain rights to participate in the major decisions of the child. This is why you should consult with a lawyer to go over all the ramifications of what you do, what you want, and your goals.