Compound Interest Calculator
See how your money grows over time with compound interest, regular deposits, inflation, and tax. Includes milestones, goal planner, and a year-by-year breakdown.
What is compound interest?
Compound interest means you earn interest not only on your original money, but also on the interest already added to your balance. Over time, this causes exponential growth β often called "the eighth wonder of the world."
How to use this calculator
- Enter your starting investment amount.
- Set your annual interest rate and investment duration.
- Choose how often interest compounds (monthly is most common).
- Add regular deposits if you plan to invest more over time.
- Use advanced options for inflation and tax estimates.
Why contribution timing matters
Deposits made at the beginning of each period earn a little more interest. Deposits at the end of each period are more conservative and common for savings accounts.
Compound interest formulas
| Formula | When to use |
|---|---|
| A = P(1 + r/n)^(nt) | Periodic compounding |
| A = Pe^(rt) | Continuous compounding |
| Simple = P + P Γ r Γ t | No compounding |
Variable meanings
- A β Final balance
- P β Starting principal
- r β Annual rate as a decimal
- n β Compounding periods per year
- t β Time in years
Important note
This calculator gives an estimate. Real returns vary β taxes, fees, inflation, and market conditions all affect actual results.