Calculator
Enter all monetary amounts in the same currency. Results do not convert currency or replace lender, tax or investment documentation.
Method and inputs
Formula: future value = P(1 + r/12)^(12y) + C[((1 + r/12)^(12y) - 1) / (r/12)]
Inputs: Initial balance, end-of-month contribution, assumed annual rate and years.
Worked example
$10,000 at an assumed 5% annual rate with $100 monthly contributions for 10 years grows to about $31,998 before taxes and fees.
Growth of $10,000 at 5% a year
| Years | Compounded yearly | Compounded monthly | Simple interest |
|---|---|---|---|
| 5 | $12,762.82 | $12,833.59 | $12,500 |
| 10 | $16,288.95 | $16,470.09 | $15,000 |
| 20 | $26,532.98 | $27,126.4 | $20,000 |
| 30 | $43,219.42 | $44,677.44 | $25,000 |
The gap between the compound and simple columns is interest earned on interest, and it widens with time. The rule of 72 gives a quick doubling estimate: 72 / 5 = 14.4 years, close to the exact 14.2 years. Inflation works the same way in reverse; at 3% a year prices double in about 24 years.
Important limits
This is a mathematical projection, not an investment recommendation or guaranteed return. It excludes taxes, fees, inflation, losses and changes in contribution or return rate.