Calculator Methodology

What these pages contain

Most calculators online are a black box: numbers go in, a number comes out, and there is no way to tell whether it used this year's tax brackets or a figure someone typed in three years ago. Every calculator here has a page that opens the box.

Each one carries the same four things:

• The formula, written out — the actual arithmetic, not a description of it.
• The steps, in the order the engine performs them, including the edge cases that change the answer.
• The assumptions, stated plainly. What the tool holds constant, what it simplifies, and what it does not model at all — because a calculator that hides its limits is worse than one that admits them.
• The sources, linked to the primary authority: the IRS, the Census Bureau, the CFPB, a state Department of Revenue. Not a summary of a summary.

These are the same documents linked from the “Full methodology & sources” line at the bottom of each calculator. They exist so you can check the work rather than trust it, and so that when a number here disagrees with a number somewhere else, you can find out which one is wrong.

Home · Home loans

Mortgage Calculator — How Tallivo computes your monthly mortgage payment, the full PITI breakdown, and the amortization schedule shown in the chart.

Home Affordability Calculator — How Tallivo turns your income, debts, and down payment into a maximum affordable home price using the lender 28/36 debt-to-income rule.

Extra Payment & Biweekly Calculator — How Tallivo compares a baseline mortgage against one with extra principal or biweekly payments, and computes the interest and time saved.

Rent vs. Buy Calculator — How Tallivo compares the multi-year net cost of renting versus buying, giving both paths the same starting capital for a fair comparison.

Mortgage Recast Calculator — How Tallivo computes your new monthly payment after a lump-sum principal payment when your lender re-amortizes the loan over the same remaining term.

Closing Cost Calculator — How Tallivo totals closing costs from your own Loan Estimate and identifies which fees you can shop.

Discount Points Calculator — How Tallivo works out whether buying mortgage discount points pays off, and when.

PMI Calculator — How Tallivo works out when private mortgage insurance ends and what it costs before it does.

Money · Everyday money

Income Tax Calculator — How Tallivo estimates your 2026 federal income tax using progressive brackets, deductions, and marginal rates.

Paycheck Calculator — How Tallivo computes your take-home pay from gross salary after federal income tax, FICA, and pre-tax deductions.

Loan & Auto Calculator — How Tallivo computes loan payments and, in auto mode, the amount financed from price, tax, fees, and trade-in.

Debt Payoff Calculator — How Tallivo simulates the snowball and avalanche debt-payoff methods month by month.

Self-Employment Tax Calculator — How Tallivo computes Schedule SE self-employment tax, the income tax on business profit, and the quarterly estimate.

Bonus Tax Calculator — How Tallivo estimates what a bonus pays after withholding, and why withholding is not the same as tax.

Lottery Tax Calculator — How Tallivo estimates what a jackpot actually pays after federal and state tax, lump sum or annuity.

Salary to Hourly Calculator — How Tallivo converts between annual salary and hourly rate, including overtime.

Invest · Investing & growth

Roth vs Traditional Calculator — How Tallivo compares the two account types after tax — and why they tie when your tax rate does not change.

FIRE Calculator — How Tallivo works out when a portfolio covers your spending — and how it tests the withdrawal rate that target depends on.

Inflation Calculator — How Tallivo converts money between any two months in the CPI record, in both directions.

Compound Interest Calculator — How Tallivo projects investment growth with compounding and recurring contributions.

Dividend Calculator — How Tallivo models dividend reinvestment (DRIP), dividend growth, and yield on cost.

Capital Gains Tax Calculator — How Tallivo computes federal tax on a stock capital gain, including the 0/15/20% long-term brackets and the 3.8% NIIT.

401(k) Calculator — How Tallivo projects a 401(k) balance with salary growth, the IRS employee contribution limit, and an employer match.

Crypto · Crypto & tax

Crypto Investing Calculator — How Tallivo projects a forward crypto position from growth and staking assumptions — no price feed, no predictions.

Crypto Income Tax Calculator — How Tallivo taxes crypto you were given rather than bought — and the cost basis it creates.

Crypto Tax-Loss Harvesting Calculator — What realising a crypto loss saves this year, and what the basis reset costs later.

Crypto Tax Calculator — How Tallivo matches crypto lots (FIFO/LIFO/HIFO) and estimates short- and long-term capital-gains tax at 2026 rates.

When these change

Each methodology page carries its own last-updated date. Tax brackets, contribution limits, and state rates are revised as the underlying authority publishes them, and the data update log records every change with its source. If you find something wrong, the corrections policy explains how it gets fixed.