Toolstia / Compound interest calculator
Compound interest calculator
Enter a starting amount, an optional monthly contribution, a yearly rate and the number of years. You get the final balance, how much you put in, how much was interest, and a year-by-year table.
An estimate that assumes a fixed rate, with each monthly contribution added at the end of the month. It ignores tax, fees and inflation. Real returns vary and are never guaranteed. This is not financial advice.
How it works
- Enter your starting amount and monthly contribution.
- Enter the yearly rate, the years and how often interest compounds.
- Read the result and open the yearly table.
How it works
With compound interest you earn interest on the interest. A starting amount of 10,000 at 5% compounded yearly grows to 16,288.95 after 10 years. Compounded monthly it reaches 16,470.09.
Monthly contributions
Each contribution is added at the end of the month. Regular saving often matters more than the starting amount: 100 a month at 5% for 10 years, with no starting amount, grows to about 15,528.
Compounding frequency
The more often interest is added, the faster the balance grows, but the difference between monthly and daily is small. Most savings accounts compound monthly or daily.
Limits of the estimate
The calculator assumes a fixed rate. Real investments rise and fall, and tax, fees and inflation reduce what you keep. Treat the result as an illustration, not a forecast.
Questions
What is the difference between simple and compound interest?
Simple interest is paid only on the starting amount. Compound interest is paid on the starting amount plus the interest already earned.
Can I leave the starting amount empty?
Yes, if you enter a monthly contribution.
Does it include inflation or tax?
No. Subtract an estimate of inflation from your rate to see growth in today's money.
Is it financial advice?
No. It is a maths tool. Speak to a qualified adviser about your own situation.