Defaults are illustrations
Growth tools start with a hypothetical 5% effective annual nominal return after fees, before tax, and 3% annual inflation. The savings-goal tool starts at 3% nominal. These are editable scenario inputs, not expected returns for a named asset or a claim about current savings-account rates.
Contributions and compounding
Deposits occur at each month-end. The monthly rate is r = (1 + annual return)^(1/12) − 1. With a starting balance P, monthly contribution M and n months, FV = P(1+r)^n + M((1+r)^n − 1)/r. At zero return the balance is simply P + M × n.
Year inputs use whole years. The timeline tools step forward month by month, up to 100 years. If the target is already reached they report zero years. If the modeled target is not reached inside the horizon they say so.
Inflation, once
Purchasing power is future balance / (1 + inflation)^years. The target in timeline calculators is a future-dollar target. The purchasing-power figure is shown separately and is not the same as targeting a million in today’s dollars.
Savings goals and retirement
The savings-goal tool solves the same monthly annuity formula for M, floored at zero when the starting balance is sufficient under the assumptions. The retirement tool divides annual spending less other income by an assumed initial withdrawal rate. Its 4% starting value is adjustable and is not a guarantee of sustainability or a safe-rate recommendation.
Income and net worth
The income timeline uses annual take-home pay, not gross salary. Savings rate is monthly income less spending, divided by that same income. Net worth is assets minus debt; the result does not subtract future sale costs or taxes and is not a measure of immediately available cash.
Business and property
Business operating profit is revenue less direct costs and overhead. Break-even and target revenue assume a constant gross-margin percentage and fixed overhead. These results exclude any costs you leave out.
For rentals, net operating income (NOI) is rent after vacancy less operating expenses. Financing and capital reserves are excluded from NOI. Cash flow subtracts mortgage principal and interest and the replacement reserve. Cap rate is annual NOI divided by purchase price. Cash-on-cash return divides annual cash flow by down payment plus closing costs and initial improvements. With no cash invested, that percentage is undefined.
What the models leave out
Investment returns, income and spending can vary. Tax, changing fees, market sequence, account restrictions, transaction costs and personal circumstances can materially alter outcomes. Calculators show rounded results while retaining precision internally. They are planning illustrations, not forecasts.
Compare the concept of compounding with the SEC’s educational calculator. Different contribution timing or rate conventions can produce different answers.