What is the Compound Interest Calculator tool?
Compound interest is interest earned on both your original money and on the interest it has already earned, so a balance grows faster the longer it is left to compound. Enter a starting amount, an annual interest rate, how many years to grow it and how often interest compounds, and optionally add a monthly contribution. The calculator shows the final balance, the total you contributed, the total interest earned, a growth chart and a year-by-year table.
How to use the Compound Interest Calculator tool
- Enter a starting amount and choose a currency.
- Enter the annual interest rate, the number of years and how often interest compounds (annually, semi-annually, quarterly, monthly or daily).
- Optionally enter a monthly contribution to see how regular deposits add to the growth.
- Read the final balance, total contributed and total interest earned, and open the year-by-year table for the full breakdown.
Features
- Final balance, total contributed and total interest earned
- Growth chart showing contributions versus interest earned
- Any compounding frequency: annually, semi-annually, quarterly, monthly or daily
- Optional monthly contributions on top of a starting amount
- Full year-by-year balance table
- Runs entirely in your browser - nothing you enter is sent anywhere
How is compound interest calculated?
Each time interest compounds, it is added to the balance, and the next round of interest is earned on that larger amount, not just on the original money. The more often interest compounds (daily instead of annually, for example) and the longer the money is left to grow, the bigger the effect, because each compounding period includes a little more interest-on-interest than the one before.
Why do monthly contributions make such a difference?
Every contribution you add starts compounding from the day it goes in, so money contributed early in the term has far longer to grow than money contributed near the end. Over many years, steady monthly contributions can add up to more of the final balance than the starting amount itself.
| Years | Balance | Interest earned |
|---|---|---|
| 5 years | $13,488.50 | $3,488.50 |
| 10 years | $18,193.97 | $8,193.97 |
| 20 years | $33,102.04 | $23,102.04 |
| 30 years | $60,225.75 | $50,225.75 |
Frequently asked questions
What compounding frequency should I choose?
Use whatever your bank, bond or investment account states - savings accounts are often compounded daily or monthly, while some bonds compound semi-annually or annually. If you are not sure, monthly is a common default and the difference between frequencies is usually small compared to the interest rate itself.
Is this a guaranteed return?
No. This calculator projects growth at a fixed interest rate that you choose. Real savings and investment returns vary year to year, and investments can lose value, so treat the result as an estimate, not a promise.
Does this account for taxes or inflation?
No. The result is the raw growth of your money before any taxes on interest or investment gains, and without adjusting for inflation. Your actual spending power in the future will be lower than the raw balance shown here.
What is the difference between this and the Loan Calculator?
This tool grows a balance upward with interest working for you (savings and investments). The Loan Calculator shows a balance paying down over time with interest working against you (loans and mortgages).
Can I use this for retirement savings?
Yes, it works for any lump sum plus regular contributions - a savings account, an investment account or a retirement account. Just use a realistic estimated annual return and remember it is a projection, not a guarantee.