Compound Interest Calculator
Calculate compound interest growth with yearly breakdown and multiple compounding frequencies.
How to Use
- Enter the initial principal (starting amount).
- Set the annual interest rate and select how often it compounds.
- Enter the investment period in years.
- Optionally add regular contributions (monthly or yearly).
- Results and the year-by-year table update instantly.
When to Use This
- Comparing a monthly-compounding deposit against a quarterly one at the same headline rate, where the year-end table makes the gap visible.
- Estimating what a recurring deposit might reach over a fixed number of whole years, with the contribution field set to a monthly amount.
- Teaching the difference between simple and compound growth, since the yearly table separates contributions from interest earned in each row.
- Setting a savings target by adjusting the rate and the period until the final value lands near the amount you have in mind.
Frequently Asked Questions
About This Calculator
Compound interest pays interest on interest, so growth is exponential rather than linear: A = P(1 + r/n)^(nt), where n is the number of compounding periods in a year. Frequency matters because each period's closing balance becomes the next period's base, which is why monthly compounding beats annual compounding at the same stated rate, by a margin that widens as the rate rises.
Rather than evaluating that formula once, this tool steps through the term year by year and period by period, which is what lets it print an annual table. Contributions are handled two ways: when they are at least as frequent as compounding, the per-period amount is added before interest is applied; a yearly contribution under more frequent compounding is added once at the end of each year. Outputs are the final value, total invested, total interest and the yearly rows.
Notes & Limits
- The term is truncated to whole years, so entering 2.5 years computes two years. Express a part-year tenure in whole years to get a meaningful result.
- When contributions are more frequent than compounding, such as monthly deposits with annual compounding, the whole year's contributions are added at the start and earn a full year of interest.
- Nothing here accounts for tax, inflation, fees or a rate that changes partway through; the rate you enter is applied unchanged for the entire term.
- The rate must be above zero, and the output is a projection from your assumptions rather than a guaranteed return on any actual product.