How We Calculate
Every number on FigureMoney comes from a published source and a formula you can check. This page lists those sources, how often we refresh them, the math behind the calculators, and the assumptions that apply to every estimate. For who builds the site, see About.
Our data sources
We use primary sources — the agency that sets a figure — whenever one exists, and name the publisher whenever we rely on survey or market data. Each calculator also lists its own sources and “last verified” date.
| Source | What we use it for | Refreshed | Last verified |
|---|---|---|---|
| IRS Revenue Procedure 2025-32 | Federal tax brackets, standard deductions, capital gains thresholds (2026) | Each fall, when the IRS publishes next year’s figures | July 2026 |
| IRS Publication 15-T and Form W-4 | Paycheck withholding method (percentage method, Worksheet 1A) | Each December–January | July 2026 |
| IRS Notice 2025-67 | 401(k), IRA, and catch-up contribution limits (2026) | Each November | July 2026 |
| IRS Rev. Proc. 2025-32 §4.05–4.06 and IRC §24 | Earned income credit table, child tax credit, and refundable child credit (2026) | Each fall, with the final Form 1040 instructions each January | October 2026 |
| IRS Publication 590-B | Uniform Lifetime Table and RMD rules | When the IRS changes the tables or rules | October 2026 |
| One Big Beautiful Bill Act (P.L. 119-21), Treasury T.D. 10044, IRS FS-2025-03 and FS-2026-13 | Tips, overtime, and senior deductions (2025–2028) | As the IRS issues forms and guidance | October 2026 |
| Social Security Administration (COLA fact sheet, Office of the Chief Actuary) | Wage base, benefit formula bend points, COLA, earnings test, maximum benefits | Each October | October 2026 |
| Tax Foundation — state income tax rates and brackets | State income tax in paycheck and salary estimates (all 50 states + D.C.) | Each January | July 2026 |
| Tax Foundation — state and local sales tax rates (midyear 2026) | Sales tax calculator and state pages | January and July | August 2026 |
| U.S. Bureau of Labor Statistics — CPI-U | Inflation calculator | Each January | August 2026 |
| Federal Reserve G.19, Bankrate Monitor, NerdWallet | Personal loan rate benchmarks and rates by credit score | Quarterly (Fed) and monthly (others) | October 2026 |
The core formulas
- Loan payments (mortgage, auto, personal, student)
- Standard fixed-rate amortization: Payment = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where r is the monthly rate and n the number of payments. Every loan calculator shares one implementation, so their numbers always agree.
- Savings and investment growth
- Compound growth with regular contributions, compounded monthly unless a calculator says otherwise. Returns you enter are assumptions, not predictions.
- Income tax
- Progressive brackets applied to taxable income (income minus pre-tax deductions and the standard deduction). Only the income inside each bracket is taxed at that bracket’s rate.
- Take-home pay
- Gross pay minus federal income tax, Social Security (6.2% up to the wage base), Medicare (1.45%, plus 0.9% over $200,000), state income tax, and pre-tax deductions. The paycheck calculator and every salary and hourly page use the same function.
Each calculator’s “How We Calculate” panel shows its exact formulas, a worked example, and the constants it uses.
Assumptions behind every estimate
- Tax estimates assume the standard deduction and no credits unless the calculator asks about them.
- State tax estimates use state brackets and standard deductions; local income taxes and state payroll taxes (such as California SDI) are not included.
- Hourly-to-salary conversions use a 2,080-hour full-time year (40 hours × 52 weeks).
- Income-based phase-outs use your total income as a stand-in for modified AGI, which matches for most wage earners.
- Social Security estimates use the latest published benefit formula; your official benefit depends on your full earnings record at SSA.
- Loan rates by credit score are averages from named sources; your offer depends on your full credit profile and lender.
Official figures vs. projections
Calculators use only official, published figures for the current tax year. When we write about next year before the government has published its numbers — such as projected tax brackets — we label the page “projected” in its title, say who made the projection, and replace the figures as soon as the official ones are released. Survey data such as average loan rates always carries its source and as-of date.
Editorial independence
FigureMoney may be supported by advertising. Advertisers have no say in our calculators, results, or articles, and we don’t accept payment to feature or rank any lender or product. Our guides explain how financial products work; they aren’t personalized advice.
Corrections
If you find a figure that is wrong or out of date, please tell us. We check every report against the original source, fix confirmed errors promptly, and record meaningful changes below.
Recent updates
- Oct. 18, 2026Added 401(k) match, Roth conversion, dividend (DRIP), millionaire, pay raise, profit margin, percentage, and tip calculators, plus a new Everyday Math section.
- Oct. 18, 2026Added debt consolidation, balance transfer, credit card minimum payment, car lease, lease vs. buy, and auto refinance calculators.
- Oct. 18, 2026Added tax bracket, earned income credit, child tax credit, bonus tax, rent affordability, and 50/30/20 budget calculators.
- Oct. 18, 2026Every calculator can now be embedded on other websites free of charge — see Embed Our Calculators.
- Oct. 18, 2026Added investment, retirement withdrawal (“how long will my money last”), Social Security break-even, loan payoff, and high-yield savings calculators.
- Oct. 17, 2026Added the 2026 Tax Refund Calculator (child tax credit, earned income credit, and Schedule 1-A deductions from Rev. Proc. 2025-32).
- Oct. 17, 2026Added the No Tax on Tips & Overtime calculator and guides to the tips, overtime, and senior deductions.
- Oct. 17, 2026Social Security estimator moved to the 2027 benefit formula ($1,340 / $8,077 bend points) after SSA’s Oct. 14 announcement.
- Oct. 17, 2026Published projected 2027 tax brackets, clearly labeled until the IRS releases official figures.
- Oct. 17, 2026Added personal loan rate benchmarks (Fed G.19, Bankrate, NerdWallet) with as-of dates.
- Oct. 17, 2026Added hourly/salary conversion pages and RMD-by-age pages built on the same verified tax and IRS table data.
Who reviews the numbers
Calculators and guides are built and checked by David Miles, who verifies each figure against its source before publishing. FigureMoney provides estimates for education and planning, not financial, tax, or legal advice — confirm important decisions with a qualified professional.