The hard part was checking their work and it was very time-consuming/tedious, so I built this Google Sheet to do the work for me!
Just input a salary, select a state and filing status, include any Traditional or Roth contributions for retirement, and even the number of paychecks per year (super handy for budgeting at different paycheck rates), and... poof! You get their paycheck amount as well as the breakdown of all the steps along the way such as how much income tax is paid in each bracket at the federal level and for the state too.
I currently have 19 states included (adding more regularly) in the sheet: Alaska, California, Colorado, Florida, Illinois, Maryland, Massachusetts, Michigan, Nevada, New Hampshire, New York, Ohio, Pennsylvania, South Dakota, Tennessee, Texas, Virginia, Washington, and Wyoming.