Compound Interest Calculator with Chart 2026
See year-by-year balance growth with a live chart. Compare monthly vs annual compounding, apply inflation adjustment, and find your Rule of 72. Free, no signup.
Enter a starting amount, annual interest rate, time horizon, and optional monthly contribution to see your balance grow year by year on an interactive chart. The calculator supports daily, monthly, quarterly, and annual compounding frequencies, applies an inflation adjustment to show real purchasing power, and displays your Rule of 72 doubling time as you type. Free, no account needed.
Final balance
$63,368
Total contributions
$40,000
Interest earned
$23,368
Effective APY
7.23%
Assumes a constant annual return. Actual investment returns vary and are not guaranteed.
Rule of 72
At 7% interest rate, your money doubles every 10.3 years.
Monthly vs annual compounding comparison
| Monthly | Annual | |
|---|---|---|
| Final balance | $63,368 | $61,121 |
| Difference | $2,247 more with monthly compounding | |
Year-by-year growth
How compound interest grows your money over time
- 1
Enter principal and monthly contribution
Set your starting balance and any recurring monthly addition. The calculator shows both lump-sum and contribution-based growth on the same chart.
- 2
Set your interest rate and time horizon
Enter the annual rate and number of years. The live chart updates immediately so you can see the exponential growth curve as you adjust inputs.
- 3
Choose your compounding frequency
Select daily, monthly, quarterly, or annual compounding to compare how frequency affects your final balance over the same time period.
- 4
Toggle inflation adjustment to see real returns
Enable the inflation rate field to view your balance in today's purchasing power alongside the nominal figure and see your true real return.
What this compound interest calculator includes
Live growth chart
Year-by-year balance displayed as an interactive visual so you can see the exponential curve and the impact of contributions at a glance.
Multiple compounding frequencies
Compare daily, monthly, quarterly, and annual compounding on the same inputs to see the exact dollar difference each frequency produces.
Rule of 72 display
Your estimated doubling time shown in years as you adjust the interest rate so you can instantly apply the Rule of 72 to any scenario.
Monthly contribution modeling
Add recurring contributions to see how regular saving accelerates growth compared to a one-time lump sum investment.
Inflation adjustment
Toggle an inflation rate to view both nominal balance and real purchasing power side by side over the full time period.
Year-by-year comparison table
Nominal and inflation-adjusted balances shown year by year so you can track exactly when your real returns cross specific milestones.
How do I visualize compound interest growth over time?
The chart above shows your balance growing year by year from your starting principal to the final amount. The green line is your nominal balance. The gray dashed line shows total principal invested, so you can see exactly how much of your final balance came from interest versus contributions. Toggle the inflation-adjusted line to see how purchasing power changes over time.
Compound interest growth is slow at first and accelerates dramatically in later years, which is why starting early matters more than the amount you invest. A $10,000 investment at 7% grows to about $20,000 after 10 years but reaches $76,000 after 30 years. The chart makes this exponential curve visible in a way that numbers alone cannot. For more detail on the math, read our compound interest guide.
What is the Rule of 72 and how do I use it?
The Rule of 72 gives you a quick mental estimate of how long it takes to double your money. Divide 72 by your annual interest rate. At 6%, money doubles in 12 years. At 9%, it doubles in 8 years. At 12%, it doubles in 6 years. The widget above calculates your specific doubling time as you adjust the interest rate input.
The Rule of 72 also works in reverse for inflation. At 3% inflation, purchasing power halves in about 24 years. This is why keeping cash in a low-yield savings account is a slow form of wealth erosion. If you carry a mortgage while investing, see how the numbers compare with our mortgage payment calculator. Knowing both your investment growth rate and your debt cost is the basis of sound financial planning.
Does monthly compounding really make a difference?
Yes, monthly compounding produces more interest than annual compounding at the same nominal rate because interest is added to the principal 12 times per year instead of once. The effective annual yield (APY) of a 6% rate compounded monthly is actually 6.17%, not 6%. Over decades, this difference compounds into thousands of dollars.
The comparison table above shows the exact dollar difference for your specific inputs. For investors, use our tax calculator for investors to understand how taxes on investment gains reduce your effective compounding rate. Net after-tax return is what actually compounds in a taxable account.
Frequently asked questions about compound interest
How does compound interest work?
Compound interest earns returns on both your original principal and the interest already accumulated. Unlike simple interest, which only earns on the principal, compound interest grows exponentially over time. The more frequently it compounds, the faster it grows.
What is the Rule of 72?
The Rule of 72 is a quick formula 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 12 years. At 9%, it doubles in about 8 years.
Is monthly compounding better than annual compounding?
Yes. Monthly compounding produces more interest than annual compounding at the same rate because interest is added to the principal 12 times per year instead of once. The difference is small at low rates but becomes significant over longer time periods.
How does inflation affect compound interest returns?
Inflation reduces your real purchasing power even as your nominal balance grows. If your investment earns 7% annually but inflation runs at 3%, your real return is roughly 4%. The inflation-adjusted toggle above shows both nominal and real growth side by side.
What is the formula for compound interest?
The formula is A = P(1 + r/n)^(nt), where A is the final amount, P is the principal, r is the annual interest rate as a decimal, n is the number of compounding periods per year, and t is the number of years.
How much does $10,000 grow in 20 years at 7%?
$10,000 invested at 7% annual interest compounded monthly grows to approximately $40,388 after 20 years. With annual compounding it reaches about $38,697. Enter your own numbers in the calculator above to see a year-by-year chart.
What is the difference between APR and APY?
APR (Annual Percentage Rate) is the stated interest rate without compounding. APY (Annual Percentage Yield) reflects the actual return after compounding over a year. A 6% APR compounded monthly equals an APY of about 6.17%.
How do I calculate compound interest with monthly contributions?
Add a monthly contribution amount in the calculator above. The tool adds your contribution each month before applying interest, which significantly accelerates growth compared to a lump sum. Even $100 per month at 7% over 30 years adds over $120,000 to your total.
What interest rate should I use for retirement planning?
Most financial planners use 6 to 7% for diversified stock portfolios over the long term, which accounts for historical average returns minus typical fund fees. Use the inflation-adjusted toggle to see real purchasing power, which typically translates to 3 to 4% real returns.
How long does it take to save $1 million with compound interest?
Starting with $10,000 and contributing $500 per month at 7% annual return, it takes approximately 35 years to reach $1 million. Starting with $50,000 and contributing $1,000 per month at the same rate takes about 25 years. Use the calculator above with your own numbers.