A projection, not a promise — the rate is held steady and tax is left out. Amounts are shown in US dollars; the maths works in any currency. Everything runs in your browser — nothing is uploaded.
Compounding more often than yearly quietly lifts the true yearly rate above the headline one — that gap is the effective annual rate. The doubling time follows from it (the “rule of 72” is its famous shortcut).
Same deposits, same years — only the rate moves. Two points of rate, held for decades, is usually worth more than doubling the deposit.
| Year | Balance | You put in | Interest earned |
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See what savings become: final balance, your total contributions and the interest earned, from a starting amount, rate, years, compounding and regular deposits — with an optional inflation view.
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See what savings become: final balance, your total contributions and the interest earned, from a starting amount, rate, years, compounding from yearly to continuous, and regular deposits — plus an optional inflation (today’s-dollars) view.
$10,000 at 10% compounded yearly for 10 years becomes $25,937.42 — $15,937 of it pure interest. Add $100 a month and the same decade ends at roughly $47,000, because the deposits themselves start earning interest too. Push the horizon to 20 years and the interest earned overtakes everything you paid in.
Growth is simulated event by event: each contribution lands on its own schedule (weekly, monthly, quarterly or yearly, at the start or end of the period), and at each compounding date the balance is multiplied by (1 + rate ÷ frequency) — so interest itself starts earning interest, which is the whole point of compounding. A deposit earns interest from the first compounding date that falls after it lands; continuous compounding instead grows the balance by e^(rate × time) between events. The final balance is split back into principal plus all contributions (what you put in) and the remainder (what growth added), and each year-end balance is kept for the table and the chart. The page also derives the effective annual rate — what the headline rate really delivers after compounding — and the doubling time, and its Today’s-$ view discounts every figure at your inflation rate so the numbers speak in today’s purchasing power.
Balances grow by the standard compound formula — each period’s interest is added to the balance and itself earns interest in later periods — with any regular contributions added at the frequency you choose. It is an illustration with a smooth assumed return, not a forecast: real investments move unevenly and charges and tax are not modelled.
Sources: SEC Investor.gov — Compound Interest Calculator · SEC Investor.gov — Introduction to Investing · Bank of England — Interest rates and Bank Rate.
Figures and rules checked against official sources — last verified 1 November 2026.
Interest paid on interest. In year one you earn interest on your deposit; in year two you earn it on the deposit plus year one’s interest. The snowball is slow at first and powerful later, which is exactly what the year-by-year table shows — and why starting early matters more than starting big.
A little: $10,000 at 10% for 10 years gives $25,937 compounded yearly, about $26,851 quarterly, about $27,070 monthly and about $27,179 daily. Frequency helps, but the rate, the amount and above all the time matter far more — chasing daily over monthly is rarely worth switching accounts for.
Each contribution lands on the schedule you pick — weekly, monthly, quarterly or yearly — and starts compounding from the first compounding date after it lands, a close model of a standing order. Start-of-period deposits land one period earlier than end-of-period ones, so they earn one extra slice of interest. Shifting a deposit by a few weeks changes the result by cents, not dollars. If you skip deposits in real life, lower the contribution to its honest average.
Tax, no — the projection is before tax. Inflation, optionally: switch Amounts to “Today’s $”, set your inflation rate, and every figure — final balance, table and chart — is discounted back to today’s purchasing power. The headline Future-$ view stays nominal, which is why a 10% nominal return is not 10% more spending power.
Yes, as an illustration: enter the average annual return you want to model. Real investments do not grow in a straight line, so treat the smooth curve as an average path, not a forecast.
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