Compound Interest Calculator

Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest which only earns on the original amount, compound interest lets your money grow exponentially over time because you earn interest on your interest.

Simple interest is calculated only on the principal amount. Compound interest is calculated on the principal plus all previously earned interest. Over time, compound interest grows significantly faster. For example, $10,000 at 5% simple interest earns $500 per year forever, while compound interest earns increasingly more each year.

More frequent compounding produces slightly higher returns. Daily compounding earns more than monthly, which earns more than annually. However, the difference between daily and monthly compounding is usually small. The biggest jump is from annual to monthly compounding.

The Rule of 72 is a quick way to estimate how long it takes to double your money. Divide 72 by the annual interest rate. For example, at 6% interest, your money doubles in approximately 72 / 6 = 12 years. This works best for rates between 2% and 20%.

Use this calculator to experiment with different monthly contribution amounts. Enter your initial investment, target time period, and expected interest rate, then adjust the monthly contribution until the final balance matches your goal.

This calculator shows gross returns before taxes and inflation. Actual returns may be lower depending on your tax bracket and the inflation rate. For a rough after-tax estimate, reduce the interest rate by your marginal tax rate.

Savings accounts typically offer 1-5% APY. Bonds return 3-6%. Stock market index funds have historically averaged 7-10% annually over long periods. Use a conservative estimate for financial planning. Higher rates come with higher risk.

This calculator is designed for savings and investments. Loan interest works similarly but includes amortization schedules where payments reduce the principal over time. For loans, the compound interest formula shows how much total interest you would owe if no payments were made.

The yearly breakdown shows your opening balance, contributions made that year, interest earned that year, and closing balance for each year of your investment. It helps you see exactly how compound interest accelerates growth over time.

Yes. This calculator is completely free, runs entirely in your browser, and requires no registration. Your financial data is never sent to any server or stored anywhere.

Enter any starting amount from $0 to millions. This is your principal — the lump sum that starts earning compound interest immediately. If you are starting fresh with no savings, leave this at zero and use monthly contributions instead.

Set a recurring monthly deposit amount. Regular contributions are the engine of compound growth for most people. Even $50 or $100 per month can grow into tens of thousands over decades thanks to compounding.

Enter any annual percentage rate. Try different rates to compare scenarios — 2% for a savings account, 5% for bonds, 7-10% for stock market index funds. The rate accepts decimals for precise modeling.

Choose how often interest compounds: annually, semi-annually, quarterly, monthly, or daily. Most savings accounts compound daily or monthly. More frequent compounding produces slightly higher returns.

Set any period from 1 to 100 years. Time is the most powerful variable in compound interest. Try extending your time horizon by just 5 years to see the dramatic difference it makes on your final balance.

Your projected total is displayed prominently with color-coded summary cards showing final balance (green), total contributions (blue), and total interest earned (purple) for instant visual comparison.

See how much of your total interest came from the initial investment versus your monthly contributions. This helps you understand the relative impact of your starting amount versus ongoing deposits.

The actual formula is displayed with your specific numbers, so you can see exactly how the calculation works. The standard formula A = P(1 + r/n)^(nt) is shown alongside your inputs and result.

A stacked bar chart shows your investment growth over time. Each bar is color-coded to show principal (green), contributions (blue), and interest earned (purple). The chart makes it easy to see how interest accelerates in later years.

A detailed table shows opening balance, contributions, interest earned, and closing balance for every year. This schedule lets you track exactly how your money grows year over year.

Copy your complete results including all inputs and outputs as formatted text. Share with a financial advisor, paste into a spreadsheet, or save to your notes for future reference.

All results, charts, and tables update immediately as you change any input. No calculate button needed — experiment freely with different scenarios and see the impact instantly.