Compound Interest Calculator
Calculate investment growth with compound interest. Enter your principal, interest rate, compounding frequency, and time to see your final balance, total interest earned, and year-by-year growth.
Principal + Contributions
$10,000.00
Interest Earned
$9,671.51
Final Balance
$19,671.51
Effective APY: 7.00% · Total return: 96.7%
Year-by-Year Growth
| Year | Balance | Interest (yr) | Total Invested |
|---|
Disclaimer: Free tool provided “as is” by MonitorGiant. No warranty or liability for any data loss, security issues, or infrastructure problems arising from use of this tool. Results are for informational purposes only. · A Free Tool by MonitorGiant
What is Compound Interest Calculator?
Compound interest is interest calculated on both your initial principal and the accumulated interest from previous periods. Unlike simple interest, compounding means your returns generate their own returns — often called the 'eighth wonder of the world'. This calculator shows you exactly how powerful that effect is over time, with optional regular contributions to model a savings or investment plan.
How to use this tool
- 1 Enter your starting principal — the initial lump sum you are investing or saving.
- 2 Set the annual interest rate (or expected rate of return for investments).
- 3 Choose how frequently interest compounds: daily compounding grows faster than annual compounding at the same stated rate.
- 4 Enter the time period in years or months. Add an optional regular monthly, quarterly, or annual contribution to model a savings plan.
- 5 Read your final balance, total interest earned, and effective APY from the summary cards. The chart and table show year-by-year growth.
When would you use this?
- Planning retirement savings — see how much a regular monthly contribution grows over 20–40 years at different expected rates of return.
- Comparing savings accounts — identical stated rates with different compounding frequencies produce different effective APYs.
- Evaluating investment strategies — visualise the long-term difference between a 6% and 8% annual return on the same starting capital.
How works
- 1
Enter your inputs
Set the principal, rate, compounding frequency, and time period. Add a regular contribution to model ongoing savings.
- 2
Review the summary cards
The three cards show your total invested, interest earned, and final balance. The effective APY accounts for compounding frequency.
- 3
Analyse the chart and table
The stacked bar chart separates principal from interest growth each year. Hover any bar for the exact balance. The scrollable table gives the full year-by-year breakdown.
All calculations run entirely in your browser. No financial data is sent to any server.
Comments & Feedback
Found a bug? Have a suggestion? We'd love to hear from you.
Related Tools
From the makers of this tool
Need deeper observability?
MonitorGiant tracks real-time AI performance, infrastructure health, and system reliability — far beyond what free utilities can show.