Free calculators for what you owe, what you keep and what you can claim — each one shows its working and cites its sources.
KnownSum covers the money questions most Americans run into: how much of a paycheck you take home in your state, what the 2026 deductions for overtime and tips are worth, what a mortgage really costs each month and how fast extra payments pay it off, and how much tax, title and registration you will pay when you buy a car.
Every figure is cited to the IRS, a state agency or the law itself, and each calculator lists its sources and the date they were last verified. Each result comes with the math shown step by step, so you can check it against your pay stub, loan statement or bill of sale. Calculations run in your browser: nothing you type is uploaded, and there is nothing to sign up for. Read how the figures are worked in our methodology, or see every official document we rely on in our sources.
Work out the 2026 federal deductions for overtime pay and tips, and how much they could add to your tax refund, using the IRS rules behind each figure.
See your take-home pay after federal and state withholding, turn a salary into an hourly rate, and work out overtime pay at time and a half.
Monthly mortgage payments with taxes and insurance, full amortization schedules, extra payments, payoff dates, and whether a recast or a refinance saves more.
Sales tax, title and registration fees when you buy a car, worked out state by state from each state’s own laws and fee schedules.
Project your 401(k) at retirement with your employer match and the 2026 IRS contribution limits, and see the tax you save.
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