Compound Interest Calculator
Calculate compound interest with customizable principal, rate, time and compounding frequency. Includes year-by-year growth table.
How to Use the Compound Interest Calculator
This calculator shows how your money grows over time with the power of compound interest. Enter your details and see results instantly — no signup required.
- Enter the principal amount — the starting sum you plan to invest or save (e.g. $10,000).
- Enter the annual interest rate — the expected yearly rate of return as a percentage (e.g. 7%).
- Choose a compounding frequency — how often interest is calculated: annually, semi-annually, quarterly, monthly or daily. More frequent compounding means slightly faster growth.
- Enter the time period — the number of years you want to project.
- Review your results — see the final amount, total interest earned and a visual breakdown. Click "Show Year-by-Year Table" for a detailed annual progression.
The formula used is A = P(1 + r/n)nt, where P is the principal, r is the annual rate, n is the compounding frequency and t is the time in years.
Frequently Asked Questions
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Over time this creates exponential growth — often called "interest on interest."
How does compounding frequency affect returns?
The more frequently interest compounds, the more you earn. For example, $10,000 at 7% annually for 10 years yields $19,671 with annual compounding but $20,097 with daily compounding. Monthly compounding is most common for savings and investment projections.
What is a realistic interest rate to use?
It depends on the investment. High-yield savings accounts offer 4–5%, bonds average 3–6%, and the S&P 500 has historically returned 7–10% annually after inflation. Use a conservative figure for long-term planning.
What is the Rule of 72?
The Rule of 72 estimates how long it takes to double your money. Divide 72 by the annual rate: at 7%, your money doubles in about 10.3 years. The rule works best for rates between 2% and 15%.
Does this calculator include contributions?
This version focuses on a single lump-sum principal and shows year-by-year growth. For calculators with monthly contributions, see our full Compound Interest Calculator.
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