Work out your parenting time first, since most states use overnights or a time share percentage in the formula. Then run your own state's official calculator, because that is the one the court and the child support agency work from. Anything else is a quick sanity check, useful for a rough idea and no more than that.
Worth knowing: Every calculator gives an estimate. Results depend on the accuracy of what you enter, and the court or child support agency has the final say on any order.
Most state formulas ask how many overnights or what share of parenting time each parent has. This free tool turns a schedule into percentages, days and hours so you are putting a real number into the calculator instead of a guess. No account needed.
Pros
Free and open in a browser, no sign up
Gives percentages, days and hours, which is what most forms ask for
Useful for testing how a proposed schedule change moves the number
Cons
It works out parenting time, not the support amount itself
You still need your own state calculator for the final figure
California uses a formula based on both parents' net incomes and the share of time each parent has with the children. The state runs its own guideline calculator, so this is the closest you will get to the figure a court starts from.
Pros
Run by the state agency and kept current with the guideline
Uses the same formula the court starts from
Free with no account
Cons
You need reasonably accurate income and tax details
Add ons like childcare and health insurance are handled separately
Texas sets support as a percentage of the paying parent's net monthly resources, stepped by the number of children. The Office of the Attorney General publishes the calculator, so the percentages are the current ones.
Pros
Official state tool from the Attorney General
Simple to run, you mainly need income figures
Free with no account
Cons
Percentage of income model, so parenting time has less effect than in other states
Florida uses an income shares model, combining both parents' incomes and dividing the support obligation between them, with overnights affecting the split once you pass the substantial time sharing threshold. The state programme is the right starting point for the current guideline and worksheets.
Pros
Official state source for guideline figures and forms
Explains how time sharing changes the calculation
Free
Cons
Less of a one screen calculator than some states, expect worksheets
Childcare and health costs are added into the calculation separately
New York applies a percentage of combined parental income, stepped by the number of children, with adjustments above the statutory income cap. The state child support site runs the official calculator and publishes the current cap figures.
Pros
Official state calculator using the CSSA formula
Current income cap and percentages built in
Free
Cons
Treatment of income above the cap is discretionary, so the estimate can move
Childcare, health and education add ons sit outside the basic figure
Pennsylvania uses an income shares model based on both parents' net incomes, with an adjustment where custody time is shared closer to evenly. The courts publish the estimator and the guideline schedule.
Pros
Published by the state court system
Reflects the current guideline schedule
Free
Cons
Shared custody adjustments only kick in past set overnight thresholds
Illinois moved to an income shares model, so the calculation looks at both parents' net incomes and the number of overnights. Healthcare and Family Services publishes the estimator and the current income conversion tables.
Pros
Official state agency source
Handles the shared parenting adjustment for 146 or more overnights
Free
Cons
You need net income, not gross, for a sensible result
Ohio uses an income shares model with a standard parenting time adjustment built into the guideline. The state child support site hosts the calculator and the worksheets courts and agencies work from.
Pros
Official state calculator and worksheets
Parenting time adjustment is part of the standard guideline
Free
Cons
Childcare and health insurance costs change the result significantly
Georgia uses income shares, with a set of schedules and deviations built into the official calculator maintained by the Georgia Child Support Commission. Courts expect the worksheet this tool produces.
Pros
Produces the worksheet courts actually use
Maintained by the state Child Support Commission
Free, though it asks you to create a login for saved worksheets
Cons
More detailed than a quick estimator, set aside some time
North Carolina uses income shares with three worksheets depending on custody arrangement, sole, joint or split. The state child support services pages hold the current guideline schedule and the calculator.
Pros
Official state source for the current guideline
Separate worksheets for sole, joint and split custody
Free
Cons
Picking the wrong worksheet gives a misleading number
New Jersey uses income shares with sole parenting and shared parenting worksheets, and overnights matter once you pass the shared parenting threshold. The judiciary publishes the guidelines and forms.
Pros
Published by the state judiciary
Separate shared parenting worksheet where overnights qualify
Free
Cons
Worksheet driven rather than a single quick calculator
Above guideline incomes are handled at the court's discretion
If your state is not listed above, this federal directory links to every state and tribal child support agency. From there you can find that state's guideline calculator, forms and contact details.
Pros
Covers every state and tribal agency
Official federal source, kept up to date
Free
Cons
It is a directory, not a calculator
Some states publish worksheets rather than an online tool
A fast state by state estimator that gives you a ballpark figure in a couple of minutes. Handy when you want a rough sense of the numbers before sitting down with the official calculator, and nothing more than that.
Pros
Very quick to run
Covers most states
Free
Cons
Simplified, so it leaves out add ons and local rules
A private estimator that ties the support figure to a parenting time calculation, which is useful in states where overnights drive the number. It sits alongside a paid parenting plan product, so expect prompts to sign up.