Compound Interest Calculator
See How Your Money Grows
Use our free compound interest calculator to see how your savings or investment grows over time. Enter your starting amount, interest rate, compounding frequency, and time period — and instantly see your final balance and total interest earned.
Last updated: May 10, 2026
WealthEngine Ultra Pro
Enterprise-grade Financial Projection Terminal
Nominal Balance
$0
Real Wealth (Today's $)
$0
Est. FIRE Age
FIRE = Financial Independence, Retire Early
Age when you can retire using the 4% rule (25x annual expenses of $40K). Assumes starting at age 30.
--
FIRE Roadmap
---
Passive Income Potential
Monthly Withdrawal (Safe Rate)
$0
How This Compound Interest Calculator Works
This calculator uses the standard compound interest formula as taught in finance and mathematics:
Understanding Your Results
- Final Balance — The total value of your investment at the end of the period, including all compounded interest.
- Principal Invested — Your original starting amount, unchanged.
- Interest Earned — Final Balance minus Principal. This is the pure gain from compounding.
APY vs APR: The Difference That Matters
Your bank may advertise an APR (Annual Percentage Rate) but credit your account using APY (Annual Percentage Yield) — and they are not the same number.
- APR — The stated annual rate before compounding effects.
- APY — The effective annual rate after compounding is applied. Always higher than APR (except for annual compounding where they are equal).
Example: A savings account with 5% APR compounded monthly has an APY of 5.116%. That extra 0.116% is real money — on $50,000, it's an additional $58/year. When comparing savings accounts, always compare APY, not APR.
Compounding Frequency Comparison
The same $10,000 at 7% APR for 10 years grows to:
- Annually: $19,671.51
- Monthly: $20,096.61
- Daily: $20,136.96
More frequent compounding means slightly more growth, but the difference between monthly and daily is minimal for most purposes.
Real-World Growth Examples
How $10,000 grows over 20 years at different realistic rates (compounded monthly):
| Scenario | Rate | After 10 yrs | After 20 yrs |
|---|---|---|---|
| High-yield savings (HYSA) | 4.5% | $15,634 | $24,402 |
| Conservative bonds | 3% | $13,494 | $18,209 |
| S&P 500 historical avg. | 7% | $20,097 | $40,388 |
| Aggressive growth (estimated) | 10% | $27,048 | $73,161 |
Past performance does not guarantee future results. S&P 500 historical average is approximate. See our Disclaimer.
Related Tools
- Loan Payment Calculator — Compound interest works against you with debt. Compare borrowing costs.
- Mortgage Calculator — Full PITI breakdown with PMI, HOA, and equity growth tracking.
- Credit Card Interest Calculator — See compound interest in action on revolving debt.
- Percentage Calculator — Calculate growth percentages and return rates.
Frequently Asked Questions
⚠️ Disclaimer: For educational purposes only. Investment returns are not guaranteed. See our full Disclaimer.