FinanceCalcs
Compound Interest Calculator
See how your money grows with the power of compound interest — and how your initial investment, monthly contributions, interest rate, and compounding frequency all work together to build wealth over time.
Works for savings accounts, investments, and any interest-bearing account — with optional monthly contributions.
Compound Interest Calculator
Compounded Interest $0
In 0 years you will have $0
- Future Value
- Total Contributions
“The strongest force in the universe is Compound Interest.”
— Albert Einstein
What is compound interest?
Compound interest is interest earned not just on your original principal, but also on all the interest you have already accumulated. Each period, your interest is added to the balance — and then that larger balance earns even more interest. Over time, this creates an accelerating snowball effect.
This is different from simple interest, where interest is calculated only on the original principal and never reinvested. With compound interest, the frequency of compounding matters — the more often interest compounds (daily vs. annually), the faster your money grows.
The real power of compound interest is time. The longer your money compounds, the more dramatic the results — which is why starting early makes such an outsized difference to your final balance.
chevron_right Learn more about compound interest on Wikipedia
lightbulb Example Compound Interest Scenario
Suppose you invest $10,000 at a 7% annual interest rate, compounded monthly, for 30 years. Without adding a single dollar more, your investment would grow to over $81,000 — more than 8 times your original amount — with over $71,000 in compounded interest.
If you also added $200 per month in contributions, your balance would grow to over $313,000 over the same 30 years — a powerful demonstration of how regular contributions amplify compounding.
Starting just 10 years earlier or increasing your rate by even 1–2% can add tens of thousands to your final balance. Use the calculator above to see how your specific numbers play out.
Many people use a compound interest calculator to project savings growth, plan for retirement, and compare the impact of different contribution and interest rate scenarios.
Compound Interest Calculator FAQs
How does compound interest differ from simple interest?
Simple interest is calculated only on your original principal — it never grows. Compound interest is calculated on your principal plus all previously earned interest, so each period your earnings base gets larger. Over long time periods, the difference between the two can be enormous.
How does compounding frequency affect growth?
The more frequently interest compounds, the more you earn. Daily compounding yields slightly more than monthly, which yields more than annual. The difference is most noticeable at higher interest rates and over longer time periods.
What is the Rule of 72?
The Rule of 72 is a quick way to estimate how long it takes an investment to double. Divide 72 by your annual interest rate to get the approximate number of years. At 6%, your money doubles in roughly 12 years (72 ÷ 6 = 12).
Does compound interest work against you too?
Yes. Compound interest works in reverse on debt — credit card balances, loans, and other liabilities compound just as investments do. This is why high-interest debt can grow quickly if not paid down, and why paying more than the minimum each month makes such a significant difference.
Compound interest terminology
Initial Investment
The original principal amount you are starting with — the money you have available to invest today.
Monthly Contribution
An optional amount added to your balance each month. Regular contributions significantly accelerate growth over time by increasing the base on which interest compounds.
Interest Rate
The estimated annual rate at which your investment grows. For savings accounts this is the APY; for investments it is your expected average annual return.
Compound Frequency
How often interest is calculated and added to your balance — annually, semi-annually, quarterly, monthly, or daily. More frequent compounding means slightly faster growth.
Future Value
The total value of your investment at the end of the time period — your initial investment plus all contributions plus all compounded interest earned.
Disclaimer: All calculators on this site are provided for informational and educational purposes only. Results are estimates based on the inputs you provide and mathematical formulas — they do not account for taxes, fees, inflation, risk, or other real-world factors that may affect financial outcomes. Past performance does not guarantee future results. Nothing on this site constitutes financial, investment, legal, or tax advice. Always consult a qualified professional before making financial decisions.
About FinanceCalcs.net — FinanceCalcs.net is a free financial calculator directory built and maintained by Ted Grajeda. The site exists to give everyone access to fast, accurate financial math — no subscriptions, no paywalls, no signup required. Every calculator runs entirely in your browser using standard financial formulas.