Compound Interest Calculator

See the power of compound growth and starting early

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Investment Details

How much and how long will you invest?
$10,000
Lump sum you're starting with (can be $0)
$500
Amount you'll add each month
20 years
Longer = more compound growth magic
⚙️

Growth Settings

Expected returns and compounding
7%
S&P 500: ~10% | Balanced: ~7% | Bonds: ~5%
How often interest is calculated and added
Used for milestone projections and starting-early comparisons
💡 Pro tip: Use 7% for conservative estimates. The market has ups and downs, but historically averages ~10% over long periods.

Your Investment Will Grow To

$284,896
In 20 years at age 50
+185% total growth

Total Contributions

$130,000
What you put in

Interest Earned

$154,896
Free money!

Interest Portion

54%
Of final balance

Effective Rate

7.23%
APY with compounding

Growth Over Time

Contributions vs Interest

🎯 When You'll Reach Key Milestones

⏰ The Power of Starting Early

If you invest $500/month until age 65:

🔮 What-If Scenarios

See how small changes can make a big difference

📊 Year-by-Year Breakdown

Year Age Contributions Interest Balance

💡 Investing Tips

📈 Start Now, Not Later

Time is your biggest advantage. Even small amounts invested early can grow significantly due to compound interest.

🔄 Automate Contributions

Set up automatic monthly transfers to your investment account. Pay yourself first before you can spend it.

💳 Increase With Raises

When you get a raise, increase your contribution by at least half the raise amount. You won't miss what you never had.

🎯 Max Out Tax-Advantaged

Prioritize 401k (especially if employer matches) and Roth IRA before taxable accounts for tax-free growth.

📐 The Compound Interest Formula

A = P(1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) - 1) / (r/n)]
A = Final amount P = Principal (initial) r = Annual rate n = Compounds/year t = Time in years PMT = Monthly payment