Compound interest calculator
Watch a starting balance and regular deposits grow, year by year, with interest on interest.
Future balance
$300,276
After 25 years
- Total contributed
- $100,000
- Interest earned
- $200,276
- Growth share
- 67%
- Multiple of contributions
- 3.00×
Year-by-year table
| Year | Contributed | Interest | Balance |
|---|---|---|---|
| 1 | $13,600 | $841 | $14,441 |
| 2 | $17,200 | $2,002 | $19,202 |
| 3 | $20,800 | $3,508 | $24,308 |
| 4 | $24,400 | $5,383 | $29,783 |
| 5 | $28,000 | $7,654 | $35,654 |
| 6 | $31,600 | $10,349 | $41,949 |
| 7 | $35,200 | $13,500 | $48,700 |
| 8 | $38,800 | $17,138 | $55,938 |
| 9 | $42,400 | $21,299 | $63,699 |
| 10 | $46,000 | $26,022 | $72,022 |
| 11 | $49,600 | $31,346 | $80,946 |
| 12 | $53,200 | $37,316 | $90,516 |
| 13 | $56,800 | $43,977 | $100,777 |
| 14 | $60,400 | $51,380 | $111,780 |
| 15 | $64,000 | $59,578 | $123,578 |
| 16 | $67,600 | $68,629 | $136,229 |
| 17 | $71,200 | $78,595 | $149,795 |
| 18 | $74,800 | $89,542 | $164,342 |
| 19 | $78,400 | $101,540 | $179,940 |
| 20 | $82,000 | $114,665 | $196,665 |
| 21 | $85,600 | $129,000 | $214,600 |
| 22 | $89,200 | $144,631 | $233,831 |
| 23 | $92,800 | $161,653 | $254,453 |
| 24 | $96,400 | $180,165 | $276,565 |
| 25 | $100,000 | $200,276 | $300,276 |
How to use the compound interest
- Enter your starting balance.
- Add the amount you plan to deposit every month.
- Enter the expected annual interest or return rate and how often it compounds.
- Choose the number of years and read the final balance and the yearly table.
About this calculator
Compound interest means you earn interest on your interest. The longer money stays invested, the more of the final balance comes from growth rather than from what you put in. This calculator separates the two so you can see it.
Regular contributions matter as much as the rate. Even a modest monthly deposit, kept up for decades, usually ends up larger than the starting balance. Try different rates to see a conservative and an optimistic outcome.
Future value
A = P(1 + r/n)ⁿᵗ + contributions grown at the same rate
P is the starting balance, r the annual rate, n compounding periods per year and t years. Monthly deposits are added at the end of each month and earn the equivalent monthly rate from then on.
Example
$10,000 at 7% a year, compounded monthly, with $300 added every month grows to about $300,000 after 25 years. You contribute $100,000; the other $200,000 is compound growth.
Frequently asked questions
Illustration only, not investment advice. Real returns vary and can be negative.
What is the difference between APR and APY?
APR is the yearly rate without compounding. APY includes compounding, so it is the real yearly growth. A 5% APR compounded monthly equals about 5.12% APY.
Does compounding frequency matter much?
Less than people think. Daily versus monthly compounding changes the result only slightly; the rate, the time and the size of your contributions matter far more.
What rate should I use for investments?
Savings accounts publish their APY. For stock investments, many planners use a conservative long-term average after inflation of around 4% to 6%. Returns are never guaranteed.
What is the rule of 72?
Divide 72 by the annual rate to estimate how many years it takes money to double. At 8%, money doubles in about 9 years.