About Compound Interest Calculator
Our Mission
We believe that understanding compound interest is one of the most important financial skills anyone can develop. Our mission is to make compound interest calculations accessible, accurate, and easy to understand — for everyone from first-time savers to experienced investors.
Every tool and guide on this site is free to use, requires no account, and runs entirely in your browser. Your financial data never leaves your device.
Why Compound Interest Matters
Albert Einstein reportedly called compound interest the "eighth wonder of the world." Whether or not he actually said it, the sentiment is accurate: compound interest is the single most powerful force in building long-term wealth. Unlike simple interest, which only earns returns on your principal, compound interest generates returns on your returns — creating exponential growth over time.
Consider this: $10,000 invested at 7% annual interest for 30 years grows to over $76,000 with compound interest, compared to just $31,000 with simple interest. That's the power of compounding in action. The earlier you start and the longer you stay invested, the more dramatic the results become. Use our compound interest calculator to see exactly how your money could grow.
What This Calculator Does
Our compound interest calculator is actually six calculators in one, each designed for a specific financial scenario:
- Basic Calculator — Standard compound interest with customizable compounding frequency (daily, monthly, quarterly, annually)
- Monthly Contributions — Add regular monthly deposits to see how consistent saving accelerates growth
- CAGR Calculator — Calculate the Compound Annual Growth Rate from a starting and ending value
- Simple vs Compound Comparison — Visualize the difference between simple and compound interest side by side
- Continuous Compounding — The theoretical maximum using Euler's number (ert)
- Savings Goal — Work backwards to calculate how much you need to save monthly to reach a target amount
In addition to the main calculator, we offer specialized calculators for 401(k) accounts, Roth IRAs, certificates of deposit, savings accounts, stock investments, and loans. Each calculator is tailored to account for the specific rules, contribution limits, and tax implications of that financial product.
Our Calculator Suite
Explore our full range of compound interest calculators, each designed for specific financial planning needs:
Our Methodology
Accuracy matters when it comes to financial calculations. Here are the standard formulas our calculators use:
Basic Compound Interest
Where A is the final amount, P is the principal, r is the annual interest rate (as a decimal), n is the compounding frequency per year, and t is the number of years. This is the standard formula used by the U.S. Securities and Exchange Commission and financial institutions worldwide.
Future Value with Regular Contributions
This extends the basic formula to account for regular periodic contributions (PMT), which is essential for realistic retirement and savings projections.
Continuous Compounding
The mathematical limit of compound interest as the compounding frequency approaches infinity. While no real-world financial product compounds continuously, this formula is important in financial modeling and provides a useful theoretical upper bound.
Compound Annual Growth Rate (CAGR)
CAGR smooths out volatility to express investment performance as a single annualized rate, making it easy to compare investments with different time horizons.
All calculations are performed client-side using JavaScript with IEEE 754 double-precision floating-point arithmetic and rounded to two decimal places for display. Our results match those of standard financial calculators and spreadsheet functions (such as Excel's FV and PV formulas).
Educational Resources
Beyond the calculators, we publish 33 comprehensive guides covering every aspect of compound interest. Our content is researched using authoritative sources including:
- SEC Investor.gov — U.S. Securities and Exchange Commission educational resources
- FDIC.gov — Federal Deposit Insurance Corporation
- IRS.gov — Internal Revenue Service (retirement account rules and contribution limits)
- FRED — Federal Reserve Economic Data (historical interest rates and market data)
- CFPB — Consumer Financial Protection Bureau
Our guides are updated regularly to reflect current interest rates, contribution limits, and regulatory changes.
Popular Guides
Limitations & Disclaimer
This calculator provides estimates for educational and informational purposes only. Important limitations to keep in mind:
- Actual investment returns vary and are not guaranteed. Past performance does not predict future results.
- The calculator assumes a constant interest rate over the entire period, which rarely occurs in practice.
- Taxes, fees, and inflation are not factored into the basic calculations unless specifically noted.
- This tool is not financial advice. Consult a qualified financial advisor for personalized guidance tailored to your specific situation.
Trusted Financial Resources
For additional financial education and official guidance, we recommend these authoritative resources:
- MyMoney.gov — U.S. government's comprehensive financial literacy resource
- FINRA Investor Education — Tools and resources from the Financial Industry Regulatory Authority
- NerdWallet — Independent financial product comparisons and reviews
- Bankrate — Current interest rates for savings, CDs, and loans
Contact
Questions, feedback, or suggestions? We'd love to hear from you.