Investing & Savings
Growth is the one part of personal finance where time does most of the work, and where small differences in rate or timing compound into large ones. These calculators separate the money you put in from the money it earns — including the awkward cases, like what a portfolio really returned once you account for everything you added along the way.
Calculators in Investing & Savings
- Compound InterestHow capital grows with contributions over timeCalculate
- Investment ReturnWhat a portfolio returned, annualizedCalculate
- ROI CalculatorReturn on investment for any outlayCalculate
- Savings GoalMonthly amount needed to reach a targetCalculate
- Retirement CalculatorWhether your savings last as long as you doCalculate
- Simple InterestP x r x t, with the compound comparison beside itCalculate
- Interest RateSolve for the return a plan actually requiresCalculate
- APY CalculatorWhat a quoted rate earns once compounding countsCalculate
- CD CalculatorMaturity value, and what breaking it early costsCalculate
- Emergency FundMonths of cover, and what closing the gap takesCalculate
- FIRE CalculatorThe number, the date, and your coast pointCalculate
Other categories
- Salary & PaycheckWhat you actually take home, and what an offer is really worth.
- Loans & DebtPayments, payoff order, and the true cost of borrowing.
- Mortgage & Real EstateMonthly payment, affordability, refinancing and equity.
- Auto FinanceFinancing, leasing, and what a car costs to keep.
- Business & AcquisitionWhat a business earns, what it is worth, what it costs to buy.
About investing & savings
Growth is the one part of personal finance where time does most of the work. A balance that compounds earns on its earnings, so the curve is not a straight line and the last decade contributes far more than the first. That is why the year somebody starts matters more than the amount they start with.
The arithmetic is not complicated. What causes trouble is measurement. Somebody who invested $10,000, added $500 a month for ten years and ended with $112,000 did not earn 27% a year, even though the first and last balance say so — most of that balance is their own money. The honest figure accounts for when each contribution arrived, and it is around 8%.
The other thing worth stating plainly: a constant rate of return is a planning tool, not a forecast. No market delivers the average every year, and for anyone drawing money down the order in which good and bad years arrive changes the outcome substantially. These calculators are explicit about that rather than presenting a smooth curve as a prediction.
What goes wrong here
Each of these costs real money, and each is avoidable once it is named.
Measuring return by dividing the balances
With contributions along the way, comparing the first balance to the last massively overstates performance, because it credits your own deposits as growth. The gap is routinely three-fold.
Optimising compounding frequency
Moving from annual to daily compounding at 8% on $10,000 over twenty years is worth about $2,900. One extra percentage point of return over the same period is worth $9,435. The frequency is worth getting right; it is not worth chasing.
Reading a projection in future dollars
A balance quoted thirty years out buys considerably less than the same number today. Judge it in today's money, which every projection here also reports.
Ignoring fees
A 1% annual fee is roughly a 1% lower return, compounded for the whole period. Enter returns net of fees or the projection is describing somebody else's account.
Questions people ask
Nobody can tell you what the next thirty years will do. A savings account pays what it pays. A diversified stock portfolio has historically averaged more over long periods, with years far worse and far better. Whatever you choose, enter it after fees, and treat the result as a way of thinking rather than a prediction.
Later than most people expect, and then decisively. On $10,000 starting, $500 a month at 7%, the growth passes the contributions in year 17 — and by year 25 it is nearly twice them. That crossover is the whole argument for starting early, and it is marked on the chart.
No. Interest, dividends and capital gains are taxed differently, and the account wrapper changes everything — a Roth and a taxable brokerage holding identical investments end up in very different places. Enter an after-tax return for a taxable account, or read the result as pre-tax.