Compound Interest Calculator
Calculate compound interest on one starting balance using an entered rate, term and compounding frequency. See projected growth and total interest.
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How this calculator works
Uses the standard compound interest formula A = P(1 + r/n)^(nt) so you can model long-term growth for super, ETFs or term deposits at yearly, quarterly, monthly or daily compounding.
How compound interest is calculated
Compound interest adds each period's return to the balance, so later returns are earned on both the original amount and earlier interest. Enter the starting balance, annual rate, term and compounding frequency to project that effect.
This version models one opening lump sum. It does not include later deposits or withdrawals, so calculate those separately or use a tool that explicitly asks for their amount and timing.
- Balance without contributions: P × (1 + r ÷ n)^(n × t)
- A higher compounding frequency can slightly increase the result
- Longer terms make the compounding effect more visible
Use a realistic return after fees and tax
A projection is only as useful as its assumptions. Investment returns can vary or be negative, while account fees, investment costs, inflation and tax can materially reduce the amount available in real terms.
Compare conservative, middle and higher-rate scenarios instead of treating one result as guaranteed. For a savings account or term deposit, use the advertised rate and confirm whether interest is calculated daily and paid monthly or at another interval.
Official sources and assumptions
Check the official or authoritative references used to review this calculator's rates, formulas and assumptions.
Frequently asked questions
Does compounding frequency matter much?
It matters more at higher rates and longer horizons, though the difference between monthly and daily is usually small.
Are returns guaranteed?
No. Investment returns vary and can be negative. This is a projection, not a promise.
Does it account for fees?
No. Subtract expected fees from your annual return for a more realistic figure.
Content responsibility
Maintained by CalcAussie and last updated 30 September 2026. Checks applied: calculation method, worked examples, Australian terminology, material assumptions, official references where an external rule applies, and user-facing limitations.
Calculator results remain estimates based on the figures entered. Check material decisions against current official information and report a suspected error so it can be reproduced and corrected.
Results are estimates only and are not financial, tax, legal or credit advice.