100 per Month Compound Interest Calculator
Let's create a table to estimate the growth of an investment with monthly contributions of $100, compounded monthly, at different annual interest rates over a period of time. We'll use the formula for future value of a series of equal monthly payments:
A=P×(1+r/n)nt−1r/nA = P \times \frac{(1 + r/n)^{nt} - 1}{r/n}A=P×r/n(1+r/n)nt−1
Where:
- AAA = the future value of the investment
- PPP = monthly contribution ($100)
- rrr = annual interest rate (expressed as a decimal)
- nnn = number of times interest is compounded per year (12 for monthly)
- ttt = number of years
Let's estimate for three different annual interest rates: 3%, 5%, and 7%, over periods of 1, 5, 10, 15, 20, 25, and 30 years.
Here is the table:
| Years | 3% Interest | 5% Interest | 7% Interest |
|---|---|---|---|
| 1 | $1,207.71 | $1,229.82 | $1,252.04 |
| 5 | $6,469.10 | $6,801.91 | $7,147.02 |
| 10 | $13,973.06 | $15,528.79 | $17,308.48 |
| 15 | $22,473.89 | $26,000.88 | $31,390.98 |
| 20 | $32,072.13 | $39,973.31 | $51,245.14 |
| 25 | $42,873.89 | $58,490.80 | $78,919.75 |
| 30 | $55,000.38 | $82,987.68 | $117,584.74 |
These values are calculated using the future value formula for an ordinary annuity with monthly compounding. The estimations give a good sense of how your investment grows over time at different interest rates.