Compound Interest Calculator
See how your savings grow when interest earns interest, with optional monthly additions.
Year-by-year growth
| Year | Put in so far | Interest so far | Balance |
|---|
How your balance is worked out
Interest is added a set number of times a year, and each time it earns interest too.
- 1
Rate each time
5% ÷ 12 = 0.4167%
- 2
Growth factor
(1 + 0.004167)120
= 1.6470 - 3
Grow your money
₹10,000
× 1.6470
= ₹16,470 - 4
Interest earned
₹16,470
− ₹10,000
= ₹6,470
Read more: the formula, a worked example, effective rate and the rule of 72
With compound interest, the interest you earn is added to your balance and then earns interest itself. The longer you leave it, the faster it grows, which is why starting early matters more than the amount you start with.
A = P × (1 + r ÷ n)^(n × t)
Here P is the starting amount, r is the annual rate as a decimal, n is how many times a year interest is added, and t is the number of years.
Worked example
10,000 at 5% a year for 10 years grows to 16,289 if interest is added yearly, and to 16,470 if it is added monthly. Adding 100 every month as well takes the total to about 31,998.
Effective annual rate
The more often interest is compounded, the more you earn at the same headline rate. The effective annual rate shows the true yearly growth: 12% compounded monthly works out to 12.68% a year.
The rule of 72
To estimate how long money takes to double, divide 72 by the interest rate. At 6% it doubles in about 12 years; at 9%, about 8.
Assumes a fixed rate, with monthly additions made at the end of each month. Taxes, fees and inflation are not included.