Compound Interest Calculator
Enter your principal, interest rate and term to calculate the future value with compounding.
How to use the Compound Interest Calculator
- Enter the Principal you are starting with and the Annual rate (%) you expect.
- Enter the Term (years) you plan to leave it for, then press Calculate.
- The future value comes back in the same unit you typed in, since no currency is assumed.
One lump sum, compounded once a year
The figure is the principal multiplied by one plus the rate, raised to the number of years, so interest is added annually and then earns interest itself. There is no box for regular contributions, and a fractional term such as 2.5 years is handled correctly.
What rate and time do to 1,000
The same starting sum over ten years at four different rates, with the number of years each rate needs to double the money. Doubling times here are exact rather than the rule-of-72 estimate.
| Annual rate | 1,000 after 10 years | Years to double |
|---|---|---|
| 3% | 1,344 | 23.4 |
| 5% | 1,629 | 14.2 |
| 7% | 1,967 | 10.2 |
| 10% | 2,594 | 7.3 |
Frequently asked questions
How often does it compound?
Annually. Compounding more frequently produces a slightly higher result at the same nominal rate.
Is tax or inflation included?
No. This is a pre-tax figure in nominal terms, so real purchasing power will be lower.
What does 1,000 grow to at 5 percent over 10 years?
1,629, so the interest comes to 629. Simple interest at the same rate would add only 500, and that gap is what compounding buys you.
How long does money take to double at 6 percent?
About 11.9 years with annual compounding. The rule of 72 estimates 12 years, close enough for a mental check at rates in this range.
Can I add a monthly contribution?
No. This works on a single lump sum left alone for the whole term; paying in every month needs a different formula.