A projection, not a promise — the rate is held steady and tax and inflation are left out. Amounts are shown in US dollars; the maths works in any currency.
Year-by-year growth
| Year | Balance | You put in | Interest earned |
|---|
See what savings become: final balance, your total contributions and the interest earned, from a starting amount, rate, years, compounding and monthly deposits.
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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 monthly deposits.
$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 period by period: your monthly contribution is added, 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. The final balance is then 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. Daily compounding runs the same loop with 365 steps a year; the table still reports one row per year end.
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.
Contributions are added each month and start compounding from the next compounding date — a close model of a monthly standing order. Shifting them by a few weeks would change the result by cents, not dollars. If you skip months in real life, lower the contribution to its honest average.
No — the projection is raw nominal growth. For a rough real-terms view, enter a rate reduced by inflation (7% growth with 3% inflation ≈ enter 4%): approximately right, and honestly labelled.
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.