The method
How it is worked out
A = P(1 + r/n)nt + C × (1 + i)mt − 1i
- P
- Starting amount
- C
- Each regular payment
- r
- Annual interest rate
- m
- Payments a year
- n
- Times interest is added a year
- t
- Years
- i
- Growth per payment, (1 + r/n)n/m − 1
Compound Interest Calculator
Project how a lump sum and regular contributions can grow when returns compound over time. The result updates as you type so you can compare scenarios quickly.
Keep in mind
What it leaves out
- TaxInterest may be taxed, and 401(k) or IRA allowances aren't applied.
- InflationThe balance is in future money, which buys less than today's.
- Fees and changing ratesCharges, and rates that move over time, aren't included.
Use the calculator to compare scenarios rather than as a guaranteed forecast.
About the Compound Interest Calculator
See how a starting balance and repeated contributions may grow as interest itself earns interest. The tool is useful for comparing savings goals or long-term investment assumptions, especially when the contribution amount, time horizon or frequency of compounding could change your decision.
How it works and an example to tryShow less
How to use the result
Choose a starting amount, annual rate, years, how often interest is added and how frequently you contribute. The calculator applies the chosen rate repeatedly and separates the final balance into your initial money, later payments and growth. A fixed rate is assumed throughout; future investment returns are uncertain and tax, fees and inflation are excluded.
Example to try
Begin with 10,000, add 100 each month and set a ten-year horizon. Try monthly versus yearly compounding without changing anything else. Then increase the regular payment to see whether saving more has a bigger effect than the assumed difference in compounding frequency.
Put it to work
Try it on a real situation
Load an example
What moves the result most
Worked out from your figures above. Tap a row to try it.
Who uses it, and when
Savers comparing accounts that pay interest monthly, quarterly or yearly, parents starting a fund for a child, and long-term investors who want to see how much of a future balance comes from growth rather than their own deposits.
Mistakes worth avoiding
- Using a rate you hope for rather than one you have actually been offered.
- Comparing accounts by compounding frequency when the difference is tiny next to the difference in rates.
- Forgetting that tax on interest and inflation both eat into the figure shown.
Questions
What does the Compound Interest Calculator do?
Project how a lump sum and regular contributions can grow when returns compound over time.
How should I use the result?
Choose a starting amount, annual rate, years, how often interest is added and how frequently you contribute. The calculator applies the chosen rate repeatedly and separates the final balance into your initial money, later payments and growth. A fixed rate is assumed throughout; future investment returns are uncertain and tax, fees and inflation are excluded.
Does TechBullion store the information I enter?
The core calculation or transformation runs in your browser. Normal website security and analytics may still record page-level events, but the tool does not need to create a public record from your inputs.
What mistakes do people make with a compound interest calculator?
Using a rate you hope for rather than one you have actually been offered. Comparing accounts by compounding frequency when the difference is tiny next to the difference in rates. Forgetting that tax on interest and inflation both eat into the figure shown.
Is the result guaranteed?
No. Use the result as a practical check or planning aid and verify important decisions with the relevant primary source, provider or professional advice.
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Calculator results are estimates based on the figures entered and are not financial, investment, legal or tax advice.