What is Compound Interest?
Compound interest is "interest on interest" — one of the most powerful forces in investing. A compound interest calculator shows you how your money grows when interest is reinvested rather than withdrawn.
Start with an initial amount, add regular contributions, and watch your wealth compound over years or decades. Compare the difference between simple and compound interest, and see firsthand why starting to invest early makes such a significant difference.
How to Use the Compound Interest Calculator
Step 1: Enter Principal
Input your starting amount — the money you invest today.
Step 2: Set Annual Rate
Enter the annual interest rate or expected rate of return (%).
Step 3: Choose Time Period
Enter how many years you plan to keep the money invested.
Step 4: View Growth
See your final amount, total interest earned, and a year-by-year breakdown of how your investment grows.
Simple vs. Compound Interest
| Type | How It's Calculated | Growth Pattern |
|---|---|---|
| Simple Interest | On the original principal only | Linear growth |
| Compound Interest | On principal + accumulated interest | Exponential growth |
Why Use Our Compound Interest Calculator?
📅 Year-by-Year Breakdown
See exactly how your balance grows each year, not just the final total.
💰 Regular Contributions
Add monthly or annual contributions to model realistic savings plans.
⚖️ Compare Scenarios
Test different rates, time periods, and contribution amounts to plan your strategy.
⚡ Instant Results
No forms, no ads getting in the way, no waiting. Get your answer immediately.
📱 Mobile Friendly
Works perfectly on phones, tablets, and desktop — calculate on the go.
🆓 100% Free
No subscriptions, no sign-ups, no hidden fees. Use it as many times as you need.
Frequently Asked Questions
Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus any previously earned interest — making it grow faster over time.
Common frequencies are annually, semi-annually, quarterly, monthly, or daily. More frequent compounding leads to slightly faster growth.
Use realistic rates based on the investment type: savings accounts (0.5–5%), bonds (3–6%), stocks (7–10% historically). Conservative estimates give a safer projection.
Compounding works best over long periods. Starting just 10 years earlier can substantially increase your final amount due to the extra compounding cycles.
Yes — the calculator can factor in regular monthly or annual contributions on top of your initial investment.
Ready to See Your Growth?
Use our free compound interest calculator now. No sign-up required, results in seconds.
Open Compound Interest Calculator →Related Calculators
Explore our other financial tools:
💷 Salary Calculator
Calculate income to fund your investments.
🏦 Loan Calculator
Understand how interest works against borrowers.
📊 ROI Calculator
Calculate return on investment.