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Figmetric / Methodology

How Figmetric calculates

No hype. No guru. Just the math — and here is the math, in the open.

Last updated: October 13, 2026

The promise

Every Figmetric calculator publishes its assumptions, its formulas, and its limitations — on the calculator page itself and summarized below. The calculations run entirely in your browser from the numbers you type; we never see your inputs. Results are educational estimates, not financial, tax, or legal advice. When an assumption matters to the answer, we say so on the page instead of hiding it.

Tax figures follow the IRS revenue procedures for the current tax year (currently 2026). Methodology notes are reviewed whenever a calculator changes.

How each calculator works

Debt Avalanche vs Snowball

Simulates every debt month by month at its fixed APR with monthly compounding. Pays minimums on all debts and aims extra payments at the highest-APR debt (avalanche) or the smallest balance (snowball), rolling freed payments forward. Assumes no new charges and no fees.

Balance Transfer Analyzer

Compares staying on your current card against a 0% promo transfer. The transfer fee is added to the balance on day one, the promo rate applies during the promo months, and any remaining balance accrues at the post-promo APR afterward. Deferred or retroactive interest is not modeled. For the state-by-state minimum-payment evidence behind Figmetric’s balance-transfer context, see the minimum-payment trap 50-state methodology.

Promo Juggler

Sequences multiple 0% cards: assumes 0% APR until each expiry date, no new charges. Each promo's required minimum is paid first out of the monthly budget; remaining dollars go to the soonest-expiring promo, and freed minimums roll forward as cards clear. The minimum-budget figure includes balances due by each deadline plus minimums owed on longer-dated promos, floored at the total of all minimums. Post-expiry interest is a simplified estimate of continuing at the same payoff pace.

Debt vs Invest

Runs two paths side by side. Path A retires debt in avalanche order at fixed APRs with monthly compounding; Path B invests at a smooth assumed monthly return. No new charges, no fees, and no taxes on investment growth.

Rent vs Buy

Amortizes a 30- or 15-year fixed mortgage monthly, with PMI modeled until 80% loan-to-value. Each simulated month, whichever side costs less (rent vs. all-in ownership cost) invests the difference at the monthly equivalent of the assumed return; the renter's starting balance includes the down payment plus buying closing costs. No mortgage-interest tax deduction (most filers take the standard deduction).

Take-Home Pay + W-4 Tuner

Uses 2026 federal brackets and the standard deduction per IRS Rev. Proc. 2025-32. The W-4 Step 2 checkbox is approximated by halving brackets and the standard deduction; FICA is annualized on FICA wages — gross salary minus payroll HSA contributions and health premiums under a qualifying cafeteria (Section 125) plan, while traditional 401(k) deferrals remain FICA wages. State withholding is computed from each state's 2026 percentage method using the same verified tables as the Year Planner — automatic state withholding treatment for 44 jurisdictions, including nine with no broad individual wage-income tax — and includes local taxes for New York City, Yonkers, and Philadelphia where they apply. Seven jurisdictions (CT, DC, GA, ME, NC, NM, UT) are manual-entry: there you copy your per-check state withholding from a pay stub, because their published methods could not be verified to a worked example. Figures are estimates — not a substitute for the IRS withholding estimator or payroll output.

Take-Home Pay Year Planner (spreadsheet)

The planner computes each 2027 paycheck in pay-stub order: gross pay, pre-tax deductions, taxable wages, federal withholding under the 2027 Percentage Method, Social Security (6.2% to the $192,300 wage base, stopping mid-check on the crossing check), Medicare and Additional Medicare, state and local withholding, employee-paid state programs, post-tax deductions, and net pay. Year-to-date balances carry across pay dates and employer changes. It covers all 50 states and DC: automatic state withholding treatment for 44 jurisdictions, including nine with no broad individual wage-income tax; CT, DC, GA, ME, NC, NM, UT use guided manual entry because their published methods could not be verified to a worked example, and the workbook says so rather than guessing. Its Tax True-Up is a simplified liability estimate, not a tax return, and the Goals layer tests each goal against per-paycheck capacity: a per-check reality ledger flags any payday where the planned set-aside exceeds that check's projected net pay.

Home Equity

Equity = home value minus mortgage balance; maximum additional borrowing = 80% of value minus balance (the standard combined-loan-to-value ceiling). New borrowing is fully amortized monthly over the selected term (5, 10, 15, or 20 years; 15 default). No fees, points, or tax effects modeled.

Compound Growth

Month-by-month simulation with contributions added at month end. Converts the annual return to a monthly-equivalent rate for the selected compounding frequency. Constant return every year; no taxes, fees, or inflation.

Roth vs Traditional

End-of-year contributions at a constant annual return with flat marginal tax rates. No contribution limits, employer match, required minimum distributions, penalties, or state-tax modeling. Contributions are compared at equal out-of-pocket cost: the input is pre-tax dollars available to save, so the Roth amount invested is reduced by today's tax rate.

FIRE Number

FIRE number = annual spending ÷ withdrawal rate. Months to financial independence are solved in closed form with monthly compounding and month-end contributions. Constant nominal return; no taxes, fees, inflation, or sequence-of-returns risk.

Refinance Analyzer

Standard amortization with monthly compounding; closing costs paid in cash. Both loans are simulated month by month over exactly the stay horizon at fixed rates — principal and interest only (no taxes, insurance, HOA, or PMI). Two breakevens are shown: cash-flow (closing costs ÷ monthly savings) and equity-adjusted — the first month the refi's remaining balance plus all payments plus closing drops below the current loan's balance plus payments, which counts the reset loan clock.

Mortgage Payoff

Fixed rate with monthly compounding; extra payments are applied to principal from the first simulated month. Baseline interest = regular payment × scheduled months − balance. No escrow, taxes, insurance, PMI, or prepayment penalties.

Student Loan Payoff

Monthly compounding at APR/12; minimums paid on every loan, with extras plus freed minimums aimed at one loan per the chosen strategy. Refinance is shown two ways: the lender's required payments, and the same aggressive monthly budget as the current plan (isolating the pure rate advantage). No new borrowing; federal-loan features (income-driven plans, capitalization, forgiveness) are not modeled.

Known limitations

  • Simplified taxes. The standard deduction is assumed for the calculators, and AMT and phase-outs are not modeled. The Take-Home Pay calculator and the Year Planner are the exception to any flat-rate shortcut: both compute state withholding from verified 2026 percentage-method tables (with guided manual entry in CT, DC, GA, ME, NC, NM, UT) and include New York City, Yonkers, and Philadelphia local taxes where they apply. A few simpler tools — Roth vs. Traditional, for one — instead use flat marginal tax rates that you enter.
  • Smooth returns. Investment growth is modeled as a constant return — no market volatility, no Monte Carlo simulation, no sequence-of-returns risk. Real markets are bumpier, which matters most for the FIRE and debt-vs-invest tools.
  • Fixed rates unless stated. APRs and mortgage rates are treated as fixed for the simulation horizon; adjustable-rate behavior is not modeled.
  • Estimates, not institutional output. Banks, lenders, and payroll systems use exact day counts, fee schedules, and withholding tables that simplified public models can't fully reproduce. Use our results for comparison and planning — verify important decisions with a qualified professional.
  • Your numbers stay yours. All calculations run locally in your browser. Figmetric never receives the figures you type into a calculator.

Sources we cite

When a calculator or guide relies on an external fact, it links the primary source. Across the site we cite: