Compound Interest Calculator
Use our free online Compound Interest Calculator to perform fast, accurate calculations with instant formulas, step-by-step arithmetic, and verified reference benchmarks.
Compound Interest & Growth Calculator
How to Calculate: The Compound Interest Calculator Formula
Where A is future accumulated balance, P is initial principal, r is nominal annual interest rate, n is compounding frequency per year, t is time in years, and PMT is monthly contribution.
Step-by-Step Calculation Guide
- Enter your initial starting investment deposit (Principal).
- Specify ongoing periodic monthly contributions.
- Set the expected annual rate of return (interest rate).
- Select your compounding interval (Annual, Semi-annual, Monthly, Daily).
- Choose investment horizon in years to see exponential compounding in action.
Practical Compound Interest Calculator Examples
Initial deposit: $10,000, $300 added monthly, 8% annual return, monthly compounding.
Initial deposit: $1,000, $500 monthly, 10% average stock market return, 30 years.
Power of Time: $500/Month at 8% Compound Return
Official reference values and benchmark classifications based on standard institutional guidelines.
| Years Invested | Total Cash Contributed | Total Interest Earned | Final Portfolio Value |
|---|---|---|---|
| 10 Years | $60,000 | $31,473 | $91,473 |
| 20 Years | $120,000 | $174,570 | $294,570 |
| 30 Years | $180,000 | $570,175 | $750,175 |
| 40 Years | $240,000 | $1,556,929 | $1,796,929 |
Frequently Asked Questions about Compound Interest Calculator
What is the Rule of 72 in compound interest?
The Rule of 72 estimates how many years it takes for your investment to double. Divide 72 by the annual return rate (e.g., at 8% interest, money doubles in 72 / 8 = 9 years).
What is the difference between simple and compound interest?
Simple interest only pays on the initial principal. Compound interest pays interest on both the principal AND all accumulated past interest.
How does compounding frequency affect returns?
More frequent compounding (e.g., daily or monthly vs annually) generates slightly higher returns because interest begins generating its own interest sooner.
Does compound interest account for inflation?
No. To estimate real purchasing power, subtract expected inflation rate from your nominal return (e.g., 8% return - 3% inflation = 5% real return).