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Compound Interest Calculator
Project how savings grow with compounding and regular contributions.
Compound Interest Calculator tool
0.00
Final balance
0.00
Total contributed
0.00
Interest earned
Growth over time
Money you put in
Interest earned
Year-by-year balance
| Year | Contributed | Interest | Balance |
|---|
Projections assume a steady rate and uninterrupted contributions, and exclude inflation, fees and tax. This is a calculator, not financial advice.
About the Compound Interest Calculator
Compound interest is interest earned on interest already earned. Over a long period it is the difference between a balance that grows in a straight line and one that curves upward. This calculator projects that curve from an initial amount, an annual rate, a compounding frequency and a term, with optional regular contributions on top.
Compounding frequency matters less than people expect. Moving from annual to monthly compounding at the same nominal rate adds a modest amount; moving from a five-year horizon to a twenty-five-year one changes the result enormously. The year-by-year chart makes that visible: the gap between contributions and interest widens slowly at first and then quickly.
The projection assumes the rate holds steady and contributions never miss. Real returns vary, inflation erodes the value of the final figure, and tax usually takes a share. Use the result to compare scenarios rather than as a prediction, and speak to a qualified adviser before making a decision about money.
How to use the Compound Interest Calculator
- Enter your starting amountThe initial investment or balance.
- Set the rate and termAnnual interest rate as a percentage, and how many years to project.
- Choose a compounding frequencyAnnually, semi-annually, quarterly, monthly or daily.
- Add regular contributionsOptionally add a monthly amount, then read the yearly breakdown and chart.
Features
- Annual, semi-annual, quarterly, monthly and daily compounding
- Optional regular monthly contributions
- Final balance, total contributed and total interest earned
- Year-by-year table of balance and interest
- Bar chart showing contributions against interest growth
- Live recalculation as inputs change
- Copy the projection summary
Who uses this tool
The compound interest calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:
- Projecting the growth of a savings account
- Comparing the effect of saving monthly against a lump sum
- Seeing how much an extra five years of compounding adds
- Understanding how compounding frequency affects a return
- Setting a realistic savings target for a goal
Frequently asked questions
What is the compound interest formula?
The balance equals the principal multiplied by one plus the periodic rate, raised to the number of periods. Regular contributions are added using the future value of an annuity, applied at the end of each period.
How much difference does compounding frequency make?
Less than most people assume. At the same nominal rate, moving from annual to monthly compounding typically adds a fraction of a percent to the annual return. Time and the rate itself dominate the outcome.
Does the projection account for inflation?
No. The final balance is in nominal terms. Inflation reduces what that sum will buy, so a long projection is worth less in real terms than the headline figure suggests.
Are taxes included?
No. Interest and investment gains are usually taxable, and the rules differ by country and account type. The projection shows the gross figure before any tax is deducted.
When are contributions added?
At the end of each compounding period, which is the conservative convention. Contributing at the start of each period produces slightly more growth.
Is this financial advice?
No. It applies a standard formula to the numbers you supply and cannot account for your circumstances, your risk tolerance or market behaviour. Talk to a qualified adviser before making investment decisions.
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