Starting early versus starting later
Run the same monthly amount over thirty years, then over twenty. The gap is far wider than the ten years of extra deposits, and that gap is compounding.
Compound Interest Calculator
Project savings growth with compounding and regular deposits.
Maintained by Roshan.
Use Compound Interest Calculator
Figures update as you type. Nothing you enter leaves this tab, and no amounts are stored.
Contributions are added every periodWith monthly compounding selected, the amount below is added every month. Interest is applied first, then the contribution, which is how most savings accounts behave.
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Browse all finance calculatorsAbout Compound Interest Calculator
Compounding is the reason saving early beats saving more later, and it is also the reason the numbers feel wrong the first time you see them. Interest earns interest, so growth is not a straight line, and the final years of a long plan add far more than the first ones. This page projects that curve for a starting balance, a rate, a term, and whatever you add along the way. It runs entirely in your browser: the figures you type are not sent anywhere, not saved, and gone when you close the tab, which matters because savings balances are nobody's business but yours.
Using Compound Interest Calculator
- Enter what you already have, the rate you expect, and how long you plan to leave it. The projection updates as you type rather than behind a button, so you can change a number and watch the effect immediately.
- Choose how often interest is applied. Yearly, quarterly, monthly, and daily are all offered because accounts genuinely differ, and the choice matters: the same nominal rate compounded monthly beats the same rate compounded yearly, because each period's interest starts earning in the next.
- Add a regular contribution if you save on a schedule. It is applied at the end of every compounding period, which is how most accounts behave. The result separates what you put in from what the interest added, so the two are never confused.
- Read the split, not just the total. The panel shows the amount contributed, the interest earned, and the interest share of the final balance. Over a long term that share is the whole argument for starting sooner.
Where compound interest calculator helps
Comparing two accounts
The same headline rate paid monthly rather than yearly ends up ahead. Enter both to see whether the difference is worth switching for.
A lump sum left alone
Set the contribution to zero to model an untouched deposit. The interest share of the total climbs steadily the longer the term runs.
Before you use the result
- A projection is not a prediction. Real rates move, and market returns are not a fixed percentage delivered evenly. Treat the output as a model of one scenario, not a forecast, and try a pessimistic rate as well as a hopeful one before making a decision.
- The figures ignore inflation entirely. A balance that looks large in thirty years buys less than the same number today. A rough way to see the real picture is to enter your expected return minus expected inflation, which projects growth in today's purchasing power instead.
- Tax and fees are not modelled. Interest may be taxable where you live, and platform or account fees come off the return. Both reduce the outcome, sometimes substantially over decades, and neither appears here.
- The maths assumes a rate that never changes and contributions that never stop. Real life includes both variable rates and missed months, and the model has no way to represent either.
Questions about Compound Interest Calculator
Are my figures stored or sent anywhere?
No. The calculation runs in JavaScript on your own device. Nothing is transmitted, nothing is saved between visits, and the site has no endpoint that could receive the numbers.
Why does monthly compounding beat yearly at the same rate?
Because interest credited in month one starts earning in month two. The more often it is applied, the more of the year each portion spends earning. The gap widens with the rate and the term.
When are contributions added?
At the end of each compounding period, after that period's interest. If you pick monthly compounding, the amount is treated as a monthly deposit.
Does this account for inflation?
No. To approximate real terms, subtract your expected inflation from the rate you enter. The result is then growth in today's money rather than future money.
Is this financial advice?
No. It is a general estimate based only on what you type, with no knowledge of your circumstances, taxes, or the actual product. Confirm anything important with the provider and a qualified adviser.
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