Compound Interest Calculator
Calculate compound interest with configurable compounding frequency.
About Compound Interest Calculator
Compound Interest Calculator estimates how a single starting amount grows when interest is added to the balance and itself earns interest. Set the principal, annual rate, time and compounding frequency to see the final amount and interest earned. It is useful for understanding why the timing of interest credits matters even when the quoted annual rate is unchanged.
This tool models a lump sum, not a stream of regular deposits. Compare annual, quarterly or monthly compounding while holding the other inputs fixed, or vary the duration to see how reinvested interest accumulates. The result describes the formula under your assumptions; it does not check a financial product’s terms, retrieve current rates or guarantee a return.
How to use Compound Interest Calculator
- Enter the starting amount
Set Principal to the lump sum being modeled.
- Set rate and time
Enter Annual interest rate as a percentage and Time (years).
- Choose compounding
Select Annually, Semi-annually, Quarterly, Monthly or Daily.
- Review the projection
Read Final amount and Interest earned. Results update as inputs change, with Copy and Print actions available.
Example: Annual compounding
A principal of 10,000 at 10% annually for 2 years becomes 12,100 with annual compounding. The first year adds 1,000; the second adds 1,100 because interest is also earned on the first year’s interest.
How it works
The calculation is A = P × (1 + r/n)^(n × t). P is the principal, r is the annual percentage expressed as a decimal, n is the number of compounding periods per year and t is the time in years. The tool divides the annual rate between the periods and applies growth for the total number of periods. Interest earned is the resulting final amount minus the original principal.
For a positive nominal rate, more frequent compounding produces a slightly larger result because credited interest begins earning interest sooner. The annual rate field is a nominal rate; entering an already-effective annual yield and also choosing monthly compounding would describe a different assumption. The Daily option uses 365 periods per year. No contributions or withdrawals are added to the balance, and the calculation does not reproduce product-specific calendar or interest-crediting rules.
When is this useful?
- Understand interest earned on a lump sum.
- Compare compounding frequencies at the same nominal rate.
- Explore the effect of reinvesting interest over a longer period.
Things to know
- This version has no regular contribution or withdrawal field.
- The annual rate stays constant; fees, taxes and inflation are excluded.
- Daily compounding uses 365 periods per year rather than a bank-specific calendar.
Privacy & processing
Principal, rate, time and frequency are evaluated by a JavaScript formula in your browser. No savings account connection or remote processing request is used.
Further reading
Frequently asked questions
How is this different from simple interest?
Simple interest applies the rate to the original principal only. Compound interest also grows previously credited interest.
Can I add a monthly deposit?
Not in this tool. SIP Calculator models fixed monthly contributions; use it when deposits are part of your scenario.
What does the annual rate represent?
A nominal annual rate that is divided by the selected number of compounding periods. It is not automatically converted from an effective annual yield.
Is the final amount guaranteed?
No. It is a mathematical projection using your fixed-rate assumption, before charges and other real-world adjustments.