Why this is not a W-4 calculator
Employers withhold from Form W-4 and IRS percentage-method tables in Publication 15-T. Those tables have not been transcribed here, so inventing a withholding figure from filing status and a paycheck would be a guess dressed as a schedule.
Enter what was actually withheld — Form W-2 box 2 — and the page compares it with tax from the ordinary brackets, Schedule SE if you enter a profit, and the same credit engines as the dedicated pages.