Free online financial tool
Compound Interest Calculator
Calculate daily, monthly, and annual compound interest instantly. Use our free online compound interest calculator with real-time charts, goal planning, and the full interest compound formula — no sign-up required.
Configure your investment
Contributions are made at the end of each period (e.g. after the month closes). Switch to Beginning if you deposit at the start — earns one extra period of interest.
Future Value
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Principal
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Contributions
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Interest
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Doubling Time ⓘ
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Total Return ⓘ
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Interest Earned ⓘ
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Effective Rate ⓘ
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Investment breakdown
Total Value
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Principal
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0%
Contributions
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Interest Earned
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Growth over time
Year-by-year breakdown
| Period | Contributions | Interest | Total Interest | Balance |
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Compare scenarios
See how different rates or contributions change your outcome.
Scenario A
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Scenario B
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Goal planner
Work backwards — enter your target and find out exactly how much to invest each month.
How to use this planner
- Target amount — the total balance you want to reach (e.g. $1,000,000 for retirement).
- Starting amount — any savings you already have towards this goal. Leave at 0 if starting fresh.
- Years — how long you have to reach the goal.
- Expected annual rate — the annual return you expect (e.g. 7% for a broad index fund).
The planner solves for the fixed monthly contribution needed so that, compounded monthly, your balance hits the target exactly at the end of the period.
You need to invest approximately
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Learn
Understanding compound interest.
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest (calculated only on the principal), compound interest grows exponentially — your money earns interest on its interest.
The formula
Where P = principal, r = annual rate, n = compounds per year, t = years, PMT = periodic contribution.
The Rule of 72
Divide 72 by your annual return rate to estimate how many years it takes to double your money. At 7% returns, your money doubles roughly every 10.3 years.
Why start early?
Time is the most powerful factor. Starting 10 years earlier — even with smaller contributions — often results in more wealth than starting later with larger amounts. This is the "snowball effect" of compounding.
Compound frequency matters
The more frequently interest compounds, the more you earn. Daily compounding yields slightly more than monthly, which yields more than annually. The difference grows with larger balances and longer time horizons.
FAQ
Frequently asked questions.
Get answers to the most common questions about compound interest — how it works, the formula, daily vs monthly compounding, the Rule of 72, APR vs APY, and more.
What is compound interest?▾
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, it grows exponentially — your money earns interest on its interest.
How do I calculate compound interest?▾
Use the formula A = P(1 + r/n)^(nt), where P = principal, r = annual rate (decimal), n = compounds per year, t = years. Or use our calculator above for instant results.
What is the Rule of 72?▾
Divide 72 by your annual interest rate to estimate years to double your money. At 8%, it doubles in ~9 years.
Popular Calculations
Explore Common Compound Interest Scenarios
$10,000 at 7% for 10 Years
Monthly compounding → $20,097
$100,000 at 7% for 20 Years
Monthly compounding → $403,966
$50,000 at 10% for 20 Years
Monthly compounding → $366,096
$500/Month for 30 Years at 7%
Build $610,000+ with consistent investing
$1,000/Month for 20 Years at 10%
Aggressive growth → $759,369
$10,000 at 5% for 30 Years
Conservative long-term → $44,677
$5,000 at 12% for 20 Years
High growth → $54,274
$200/Month for 30 Years at 7%
Small amounts, big results
$1,000,000 at 5% for 10 Years
Preserve wealth → $1,647,009
About This Tool
The Best Free Compound Interest Calculator Online
Welcome to InterestCompound.com — a free, fast, and accurate compound interest calculator designed for savers, investors, and anyone who wants to understand how their money grows. Whether you're planning for retirement, saving for a down payment, or simply exploring the power of compounding, this tool gives you real answers in real time.
What Is the Interest Compound Formula?
The interest compound formula is the mathematical expression that calculates how money grows when interest is added back to the principal and earns more interest over time. The standard formula is:
Where A is the final amount, P is the principal, r is the annual interest rate, n is the number of times interest compounds per year, and t is time in years. Our online compound interest calculator handles this formula automatically — just enter your numbers and see results instantly.
Daily, Monthly, and Annual Compound Interest
The frequency at which interest compounds makes a real difference to your final balance. Our daily compound interest calculator computes growth using 365 compounding periods per year — the standard used by most high-yield savings accounts and money market funds. Use the monthly compound interest calculator mode for loans, CDs, and investment accounts that compound 12 times per year. The annual compound interest calculator mode is ideal for bonds, fixed deposits, and long-term projections.
The difference between daily and annual compounding on a $10,000 balance at 5% over 10 years is over $120 — small day-to-day, but it adds up. That's why knowing your compounding frequency matters, especially for bank interest compound calculator use cases like CDs and savings accounts.
Continuous Compound Interest
Our continuous compound interest calculator uses Euler's number (e) to model interest that compounds infinitely often — the theoretical maximum compounding rate. The formula is A = Pe^(rt). While no bank offers truly continuous compounding, it's a useful benchmark for comparing financial products and understanding the upper limit of interest growth.
Features of This Online Compound Interest Calculator
- Supports daily, monthly, quarterly, and annual compounding frequencies
- Add regular contributions (weekly, bi-weekly, monthly, or yearly)
- Adjust for inflation to see real purchasing power over time
- Interactive growth chart to visualize principal vs. interest earned
- Comparison mode to contrast two investment scenarios side by side
- Goal planner: find out how much to invest monthly to reach a target
- Export results as CSV, PNG, or print-ready summary
Why Compounding Frequency Matters for Investors
Using a daily interest compound calculator versus a monthly one reveals the true cost and return differences across financial products. A savings account advertised at 5% APR compounding daily actually yields an APY of about 5.13%. Over decades, this seemingly small gap compounds into thousands of dollars. Smart savers use an interest compound calculator to compare products before committing.
Who Should Use This Calculator?
This online compound interest calculator is built for everyone — students learning about the interest compound formula, first-time investors evaluating savings accounts, parents planning college funds, and retirees stress-testing their nest egg. No account required, no ads, no paywalls. Just a clean, accurate, and fast compound interest calculator that works on any device.
Bookmark this page and return whenever you need to run quick projections. The tool updates instantly as you type — no page reloads, no waiting.
Disclaimer
This calculator is for illustrative and educational purposes only. It does not constitute financial advice, investment recommendations, or tax guidance. Actual returns will vary based on market conditions, fees, taxes, and other factors not modeled here. Consult a qualified financial advisor before making investment decisions.
Future Value
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InterestCompound.com