Compound Interest Calculator
See how your savings or investments grow over time. Add monthly contributions, toggle inflation adjustment, and visualize your growth year by year.
Final balance
$301K
Total contributions
$130K
Interest earned
$171K
Money doubles in
10.3 yrs
Inflation adjustment
Show real purchasing power
Balance after 20 years
$300,851
$130,000 contributed · $170,851 earned
Rule of 72
At 7% your money doubles every 10.3 years (exact: 10.2 years). Over 20 years it doubles approximately 1 times.
Stacked bars show your starting amount, contributions, and interest earned — year by year.
Disclaimer: The results provided by this calculator are estimates for informational purposes only and do not constitute financial, legal, or tax advice. Actual loan terms, interest rates, monthly payments, and total costs will vary based on your credit profile, lender, and other factors. Property tax rates shown are state averages and may differ from your local rate. FHA mortgage insurance premiums (MIP) are based on current HUD guidelines and are subject to change. Always consult a licensed mortgage professional or financial advisor before making any borrowing decisions. HitCalc is not a lender and does not offer mortgage products.
Frequently asked questions
What is compound interest?
Compound interest is interest calculated on both your initial principal and the accumulated interest from previous periods. Unlike simple interest which only grows your original deposit, compound interest causes your money to grow exponentially over time — often called 'interest on interest'.
How often does interest compound?
Interest can compound daily, monthly, quarterly, or annually. The more frequently it compounds, the faster your money grows. For example, $10,000 at 5% compounded daily grows slightly faster than at 5% compounded annually. Most high-yield savings accounts compound daily.
What is the Rule of 72?
The Rule of 72 is a quick mental math shortcut to estimate how long it takes to double your money. Divide 72 by your annual interest rate. At 6% interest, your money doubles in approximately 72 ÷ 6 = 12 years. At 8%, it doubles in about 9 years.
How does inflation affect my savings?
Inflation erodes the purchasing power of your savings over time. If your savings account earns 4% but inflation runs at 3%, your real return is only about 1%. Our inflation toggle shows you both your nominal balance (the number in your account) and your real balance (what that money can actually buy in today's dollars).
What is a good interest rate for a savings account?
As of 2025, high-yield savings accounts (HYSAs) are offering 4–5% APY, significantly higher than the national average of around 0.5% at traditional banks. For long-term investments, the S&P 500 has historically returned an average of about 7% annually after inflation.
How much will $500 a month become in 10 years?
Contributing $500/month for 10 years at a 5% annual return compounded monthly grows to approximately $77,600 — of which $60,000 is your contributions and $17,600 is interest earned. At 7%, the same contributions grow to about $86,400. Use our calculator to model your exact scenario.