Compound Interest Calculator
Future Value of Investments
$
%
yrs
$
Enter your investment details to see how your money grows.
Future Value
$0
after 10 years
BreakdownAmount
Initial Investment$0
Total Contributions$0
Total Interest Earned$0
Future Value$0
Growth by Year
Interest Rate
0%
Total Invested
$0
Interest %
0%
Doubling Time
-
Ad · 300×250
How Compound Interest Works
Compound interest means you earn interest not just on your principal, but also on the interest you've already earned. Einstein allegedly called it "the eighth wonder of the world" — and the math backs that up.
The formula: A = P(1 + r/n)^(nt) where P = principal, r = annual rate, n = compounds per year, t = years. With monthly contributions, each payment compounds for the remaining time.
A simple example: $10,000 at 7% annually for 30 years grows to $76,123 with no contributions. Add $200/month and it becomes $303,219 — over $220,000 in interest earned on just $82,000 invested.
For informational purposes only. Actual investment returns vary and are not guaranteed. Past performance does not predict future results.
Ad · 728×90
Compound Interest Questions
What is the difference between compound and simple interest?+
Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus all previously earned interest. On $10,000 at 7% for 10 years: simple interest gives $17,000. Compound interest (annually) gives $19,672 — that extra $2,672 is the "compound effect." The longer the time horizon, the larger the difference.
How often should interest compound for best results?+
More frequent compounding = more growth. Daily compounding earns slightly more than monthly, which earns more than annually. However the difference is smaller than most people think — on $10,000 at 7% for 10 years, daily vs annual compounding adds only about $18. The interest rate and time period matter far more than compounding frequency.
What is the Rule of 72?+
The Rule of 72 gives you a quick estimate of how long it takes to double your money: divide 72 by the annual interest rate. At 7%: 72/7 = about 10.3 years to double. At 10%: 72/10 = 7.2 years. At 6%: 72/6 = 12 years. It's a mental shortcut — not exact but surprisingly accurate for rates between 6-10%.
What is a realistic compound interest rate?+
For planning purposes: S&P 500 index funds have returned approximately 10% annually before inflation (7% after inflation) over the long term. High-yield savings accounts currently offer 4-5%. Certificates of Deposit (CDs) range from 4-5.5%. Bonds average 3-5%. Our calculator defaults to 7% as a conservative long-term equity estimate.
How much should I save each month to become a millionaire?+
Starting from $0 at 7% annual return: $500/month for 33 years, or $1,000/month for 24 years, or $200/month for 43 years. Starting earlier is far more powerful than saving more — $200/month for 40 years ($96,000 invested) grows to about $528,000. Start at 25 instead of 35 and the same $200/month reaches over $1 million by 65.
Does compound interest work against you too?+
Yes — credit card debt is compound interest working against you. A $5,000 credit card balance at 20% APR compounding daily, with only minimum payments, can take over 15 years to pay off and cost over $7,000 in interest. This is why paying off high-interest debt always beats saving at lower rates.