Compound interest calculator
See your future balance and interest earned.
Example plan · try your own numbers
Your projected balance
Enter your numbers to see the possibilities.
Growth chart & what-if
Save, export & assumptions
Estimates only. Assumes unchanged rates, no withdrawals, tax or fees. Monthly approximation; your bank’s daily calculation and product rules may differ. Calculation details →
See the numbers behind the picture
Your interest earns interest.
Leave the interest with your savings. Next year, both can earn a little more.
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You start
$100
The money you put in.
Your starting savings
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One year later
$105
You earn $5. Keep it in.
$100 + $5 interest
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Another year
$110.25
Now all $105 earns interest.
$105 + $5.25 interest
Where did the extra 25¢ come from?
Your original $100 earns $5 again.
Last year’s $5 interest earns another 25¢.
Interest earning interest. That’s compound interest.
AUD · Teaching example: 5% a year, added once a year and left in the account. No extra deposits, withdrawals, fees or tax. This is not a bank offer or a guaranteed return.
The calculator above adds interest monthly, so its results will differ from this yearly example. See more simple examples →
How it works & common questions
Let time work with your savings.
A savings balance has three building blocks: the money you start with, the deposits you add and the interest your account earns. Change one input at a time to see which part has the biggest effect on your plan.
How this calculator works
We add interest to the opening balance each month, then add your monthly contribution. Weekly contributions use 52 payments a year and fortnightly contributions use 26, spread across 12 months. The annual table separates your deposits from interest.
View formulas and limitations →
Further reading: ASIC’s Moneysmart ↗
A few good questions.
Are the bank rates live?
The bank picker uses dated snapshots of public CDR product data. Each product shows when we retrieved it. Rates can change after that date; check the provider before making a decision.
Does the calculator include bonus interest?
The picker starts with a supported base rate. For supported bonus or introductory offers, you can check the published conditions and explicitly choose a conditional scenario. It assumes you meet those conditions; it does not assess eligibility. Supported welcome rates end after their stated period, then return to the base rate. Unsupported offers require manual checking. A rate you type yourself stays constant for the whole projection.
Why might my bank pay a different amount?
Many banks calculate interest daily and credit it monthly. Actual deposit dates, differing month lengths, rounding, balance tiers, fees, withdrawals and bonus conditions all affect the result. This is a monthly planning approximation.