· Calculators

Calculators that do the actual math for you.

Type your numbers and get the real answer, in plain English. Then open the math to see exactly how we got there. No signup, nothing to install, and every figure shows its work.

21free calculators, from paychecks and taxes to compounding, mortgages, and the real cost of waiting

Every calculator shows its work.

Most calculators online just hand you a number. Ours open up. Under every tool you get four things, always.

01

The formula

The exact math each calculator runs, written out on the tool page, not hidden behind a black box.

02

The assumptions

Every rate, rule, and default we assumed, stated plainly so you can check them against your own situation.

03

The limitations

What the tool does not account for, listed openly. A calculator is a model, not your whole life.

04

What it is NOT

An honest boundary on what the number means. It is a plain-English estimate, never personalized advice.

All 21 calculators

21 calculators · free, in plain English, every figure sourced or shown

SourcedThe Trump Account Real Cost CalculatorSee what a Trump Account's $1,000 government seed is actually worth: the poster projection next to the same balance in today's dollars, before tax.Open The 18th Birthday RevealProject a 529 plan and a UTMA / UGMA account side by side from a child's birth to the state's age of majority, with a what-happens-at-18 trade-off card.Open The Real Cost of Waiting, Kid EditionSame monthly contribution, three start ages (birth, 5, 10). The dollar gap at 18 is the compounding cost of waiting.Open SourcedKiddie Tax Estimator (2026 bands)Federal kiddie tax split across the three 2026 IRS bands per Rev. Proc. 2025-32 Sec. 4.02. Education only, not a tax return.Open Retirement Reality CheckA free Monte Carlo simulator. Run your retirement plan 1,000 times against different market histories and see the full range of outcomes.Open The Real Cost CalculatorTurn any recurring expense into its 30-year compounded opportunity cost. The most visceral way to understand compounding.Open SourcedPaycheck CalculatorHourly or salaried. Full deduction stack (401k, HSA, FSA, custom). See where every dollar of gross actually goes.Open EmbeddableCompound growth calculatorSee how time, contributions, and rate of return shape long-term outcomes.Open EmbeddableSavings account comparisonThe same deposits in checking, regular savings, and high yield savings, side by side. See what the account choice alone is worth.Open Mortgage calculatorMonthly payment, total interest, and how extra principal payments help.Open Loan payoff calculatorSnowball vs. avalanche, model your debt payoff side by side.Open SourcedCredit card payoff calculatorWhat an extra $25/month actually saves you on a credit card balance.Open Dollar-cost averaging calculatorCompare lump-sum investing vs. spreading contributions over time.Open Asset allocation calculatorHow a stock/bond mix would have performed historically.Open SourcedTake-home pay calculatorWhat's actually left after federal, state, and FICA withholdings.Open SourcedTax bracketsSee how 2026 progressive tax brackets actually work, marginal vs effective rate, visualized.Open Rent vs. Buy calculatorCompare both paths as bundles of cash flows over your horizon. Includes property tax, insurance, PMI, maintenance, HOA, selling commission, and the opportunity cost of the down payment.Open SourcedThe Real Cost of Mortgage InsuranceFHA MIP versus conventional PMI on the same loan: what each costs per month, when it ends, and the compounded difference over 30 years.Open

Looking for worksheets, quizzes, or games too? They live on the Money Tools hub. Every calculator here is education only, never personalized financial advice.