How it works
How the Compound Interest Calculator works
Quick answer: $10,000 at 6% compounded monthly grows to $18,194 in 10 years, earning $8,194 in interest without any extra deposits.
Formula
A = P(1 + r ÷ n)^(n × t)
With monthly deposits, each deposit compounds from the month it is added.
P is the starting principal, r the annual rate, n the compounding periods per year, and t the years.
Worked example
$10,000, 6% a year, compounded monthly, 10 years, no deposits. Future value: $18,194. Interest earned: $8,194 (81.9% total growth).
$10,000 at 6% compounded monthly
| Years | Future value | Interest earned | Open |
|---|
| 5 years | $13,489 | $3,489 | Open |
| 10 years | $18,194 | $8,194 | Open |
| 20 years | $33,102 | $23,102 | Open |
| 30 years | $60,226 | $50,226 | Open |
| 40 years | $109,575 | $99,575 | Open |
Assumptions and limits
- Assumes a constant rate. Real investment returns vary year to year.
- Taxes, fees, and inflation are not deducted.
Frequently asked questions
What is compounding frequency?
How often interest is added to the balance each year; more frequent compounding grows slightly faster.
Does this include extra deposits?
It projects growth of the starting principal over the term at the given rate.
What is the Rule of 72?
Divide 72 by the annual rate to estimate the years to double. At 6%, money doubles in about 12 years.