How every number is computed

How to read a result

Every result on this site should let you answer four questions: what is the formula, what happens when I put in my numbers, what is assumed, and where did the constants come from? Tool pages show the formula and a worked example using your own inputs, list their assumptions, and cite dated primary sources.

“Checked against worked examples” has a specific meaning here, described on the verification page: the calculation is reproducible and its answers match worked examples recomputed independently of the code. It is our own testing, not a third-party audit, and it does not mean professional advice.

Your seven numbers

These are saved only in your browser (see Privacy). Defaults are a median-household starting point so every page shows a real answer before you touch anything.

Financial independence (FI)

The target

FI number = annual spending ÷ 4%, which is 25 times your spending. It comes from the 4% guideline (Bengen 1994; the Trinity Study, 1998): historically, withdrawing 4% of a portfolio in the first year, then adjusting for inflation, has usually lasted 30 years.

The date

Start with your invested balance. Each month, grow it at the real return: 7% a year before inflation, less 3% inflation, about 3.9%, so every figure is in today's dollars. Then add that month's savings: your take-home pay after tax, minus your spending, to the nearest $100 (a 401(k) contribution counts as saved). FI age is your age plus the years until the balance reaches the FI number, rounded to the nearest year, stopping the search after 60 years. It is the same calculation as the FIRE Calculator.

After FI

The net-worth curve on the map assumes you withdraw your annual spending each year, and the remainder keeps growing at the same 3.9% real return.

What this ignores

• Taxes on withdrawals and investment gains.
• Social Security, pensions, and other income.
• Changes in income or spending over time, and market ups and downs (the simulation tools cover the last one).

Savings rate, cushion, and the 401(k) match

• Savings rate = what you save ÷ (what you spend + what you save), where what you save is take-home pay minus spending (the FIRE Calculator's definition).
• Cushion = cash ÷ monthly spending. The target is six months of spending, so the gap is half of annual spending minus your cash.
• Unclaimed match = (6% − your contribution rate) × income. This assumes your employer matches 100% of contributions up to 6% of pay, which is common but varies by plan. Check yours.

Take-home pay and marginal tax rate

The quick estimate models a single filer using the 2026 federal brackets (10%, 12%, 22%, 24%, 32%, 35%, 37%; IRS Revenue Procedure 2025-32) after the $16,100 standard deduction and after your 401(k) contribution (the slider is a percent of pay, capped at the $24,500 annual limit, IRS Notice 2025-67), plus payroll tax of 6.2% on wages up to $184,500 and 1.45% on all wages, and the 0.9% additional Medicare tax above $200,000. The 401(k) contribution lowers income tax but not payroll tax. “Take-home” is what is left after tax and after that contribution.

It leaves out state and local income tax, other pre-tax deductions (HSA), credits, other filing statuses, and any income that is not wages. Real take-home will differ. Tool pages that need precision use the fuller tax tables named on their own pages.

Credit card payoff

The estimate assumes 22% APR (typical of cards that carry a balance; check your statement) and a minimum payment of the greater of 3% of the balance or $25. The “extra” scenario adds $300 a month to that payment. Time to payoff comes from the standard loan-amortization formula, and interest is total payments minus the starting balance.

Home ceiling

The ceiling is the price whose full monthly cost (loan payment, property tax and insurance) fits the lender limits: 28% of gross monthly income for housing and 36% for housing plus your other debt payments (taken as 3% of your card balance, at least $25), whichever is lower. It assumes a 30-year fixed mortgage at 7% (Freddie Mac’s 30-year average was 7.03% for the week of September 24, 2026) with 20% down, property tax of 0.89% of the price a year and $1,569 of insurance a year. HOA dues are not included, and at 20% down there is no mortgage insurance. It is the same calculation as the Home Affordability Calculator, rounded down to the nearest $1,000, and a planning estimate rather than a pre-approval.

Simulation tools (Monte Carlo)

Simulation tools test a plan against thousands of possible market histories instead of one average. Each year of each path draws a return from a normal distribution set by your stock/bond mix, applies your withdrawal, and records whether the money lasts. The success rate is the share of paths that finish above zero.

• Returns are in real (after-inflation) terms, and spending stays flat in today's dollars.
• The random seed is fixed, so the same inputs always give the same answer.
• Each tool page states how many paths it ran and the return and volatility assumptions it used.
• Limits: yearly returns are independent, a normal distribution understates extreme crashes, and spending does not flex in bad years. Real retirees adapt, which usually improves outcomes.

How the Money Map ranks steps and scores you

Each step gets a dollar-weighted priority: for example, years saved × your annual spending for a higher savings rate, interest saved for a debt payoff, or the unclaimed match. Your chosen goal multiplies its matching steps by 1.6. Steps you mark done drop to the bottom.

The score (0–100) is:

clamped to 5–99. It is a compass for your own progress, not a credit score or a benchmark against other people.

Primary sources

Individual tool pages list the sources for their own constants, with dates.

Limits, and how to correct us

These are estimates for learning and planning, not advice (see the terms). If you think a formula, assumption, or source is wrong, please tell us at support@moneyvibe.ai. Confirmed fixes are logged on the verification page.