Free Online Compound Interest Calculator
Enter your principal, interest rate and time horizon to see how your money grows with daily, monthly or annual compounding. Everything runs locally in your browser — the numbers you type are never uploaded.
Choose a calculator
Compound Interest Calculator
Enter principal, annual rate and years, pick annual, monthly or daily compounding, and see the final balance, total interest, a growth chart and a yearly breakdown.
Regular Investment Calculator
Built for monthly savings plans and recurring contributions: see how regular deposits compound over the years, with contributions and growth compared side by side.
Present / Future Value Calculator
Two modes in one tool: project today's principal forward to a future value, or work backwards from a savings goal to the amount you need to invest today.
Why compound interest matters
Time is on your side
At the same rate, the longer you stay invested, the larger the share of growth that comes from interest earning its own interest — and long horizons make a striking difference.
Frequency changes the result
Annual, monthly and daily compounding all give different effective returns. This calculator lets you compare them in one click.
A curve you can see
A chart beats an abstract formula. Every result comes with a growth curve and a detailed yearly table.
Private by design
All calculations run locally in your browser. Nothing you enter is uploaded or stored.
Latest guides
- What is compound interest? Interest on interest, in plain language
- Compound vs simple interest: the difference in one table
- The compound interest formula explained, symbol by symbol
- How to use the calculator: inputs that match real life
- Regular investing pitfalls: 5 details people get wrong
- The Rule of 72: estimating doubling time in your head
Frequently asked questions
Is this calculator free?
Yes, completely. No registration, no download — just open the page and use it.
Are the results accurate?
The calculator uses standard compound interest formulas and matches textbook results. Real products differ in day-count conventions, holidays, fees and taxes, so treat the output as an estimate.
Do you recommend financial products?
No. We only provide math tools and educational content. We do not sell or recommend products and we do not give investment advice.