Child support in Massachusetts is calculated using the Massachusetts Child Support Guidelines.
The Massachusetts Child Support Guidelines are the legal guidelines published by the Probate and Family Court Massachusetts Court System every four years which defines income standards, outlines factors considered in setting the amount of child support, and various grounds for a deviation/modification.
Judges use the Child Support Guidelines Worksheet to figure out how much child support to order, but they have the discretion to deviate up or down from the guideline amount if they have a good reason to.
The 2021 Child Support Guidelines worksheet can be found here.