Tools
Run your own numbers
Free calculators that work entirely in your browser. Nothing you type is sent anywhere, and every one of them shows its working.
Tax and withholding
The ones a spreadsheet makes miserable: thresholds that interact, cliffs that cost four figures for a single dollar, and withholding rates that were never meant to match your bracket.
Calculator
2026 figuresTax Threshold Headroom
Find out how much more you can realize this year before you cross a line that costs you.
Calculator
2026 figuresRSU Withholding Estimator
See whether the flat 22% withheld on your vesting shares leaves you owing in April.
Calculator
2026 figuresTwo-Earner W-4 Fixer
Why a two-income household owes money every April, and the exact figure to put on the form.
Calculator
2026 figuresQuarterly Estimated Tax
Work out what a freelancer or 1099 earner has to send the IRS, four times a year.
Calculator
2026 figuresS-Corp Salary vs Distribution
Find the salary that costs you least — and see what the popular saving figure leaves out.
Calculator
2026 figuresRental Property Sale Tax
The gain on a rental arrives in two pieces, taxed on two schedules. Price both before you sign.
Calculator
2026 figuresJob Offer Comparison
Compare two job offers after tax, FICA, housing, and cost of living — not just gross salary.
Housing
Two decisions with more moving parts than anybody can hold in their head, and where the popular answer — buy, and pay it down early — is right often enough to be dangerous.
Calculator
Recast vs Extra Payment vs Refinance
You have a lump sum and a mortgage. Compare all four things you could do with it, on one axis.
Calculator
2026 figuresRent vs Buy Break-Even
How many years you have to stay for buying to have been the better move.
Calculator
Mortgage Calculator
Your monthly payment, broken into principal, interest, taxes, insurance, PMI, and HOA — plus the full amortization schedule.
Retirement timing and limits
How much you are allowed to put in, and when to start taking it out. Both are arithmetic; both are widely got wrong by a margin measured in years or tens of thousands of dollars.
Calculator
2026 figuresMega-Backdoor Roth Room
How much after-tax money your 401(k) will still take this year, and what converting it is worth.
Calculator
Social Security Break-Even
Claim at 62, at full retirement age, or at 70 — and see how long you have to live for waiting to pay off.
Calculator
Coast FIRE Number
How much you need invested today for compounding alone to finish the job — and when you get there.
Calculator
Retirement Calculator
Where your savings are headed versus what your retirement income goal actually requires — both worked in today's dollars.
Saving, investing, and debt
Long-run arithmetic. What a balance becomes, what the income side is worth, and the cheapest order to clear what you owe.
Calculator
Debt Payoff Calculator
Plan every debt at once and get the cheapest order to clear them in.
Calculator
Interest Calculator
Project how a lump sum plus regular contributions grows over time.
Calculator
Stock Calculator
Project a share position with both sides of the return: price growth and dividends.
Calculator
Credit-Card Annual-Fee Calculator
Price a premium card's rewards and perks against what a simple no-fee card would have earned.
Calculator
I Bond vs HYSA vs CD/T-Bill
Compare three ways to park a lump sum for a known horizon, after tax and after the fine print.
Calculator
HYSA Emergency Fund Calculator
Turn your own essential expenses into an emergency fund target, and see how long a HYSA takes to get you there.
Calculator
Auto Loan Calculator
Price a car loan after a trade-in and sales tax — the two things a dealer's monthly payment quote usually obscures.
Calculator
Loan Calculator
The payment and full amortization schedule for any fixed-rate installment loan — personal, student, or anything else with a term.
Calculator
Payment Calculator
Know three of loan amount, payment, rate, and term? Solve for the fourth.
Calculator
Inflation Calculator
What today's dollar amount will cost in the future, and what it's already lost sitting in cash.
Calculator
Mutual Fund Calculator
Project a fund position and see exactly what its expense ratio costs you by the end.
Calculator
Compound Interest Calculator
The same nominal rate, compounded annually, monthly, or daily — see exactly how much frequency alone is worth.
Calculator
Simple Interest Calculator
Interest on the original principal only — the one calculation that never compounds — and what compounding would have added.
Calculator
ROI Calculator
Total return and annualized return on any investment — a rental, a business, a portfolio — from cost and current value.