Compound Interest Calculator
See how your money grows with compound interest.
Final Balance
$92,480.05
| Year | Opening | Contributions | Interest | Closing |
|---|---|---|---|---|
| 1 | $10,000.00 | $1,200.00 | $762.16 | $11,962.16 |
| 2 | $11,962.16 | $1,200.00 | $904.00 | $14,066.16 |
| 3 | $14,066.16 | $1,200.00 | $1,056.10 | $16,322.27 |
| 4 | $16,322.27 | $1,200.00 | $1,219.20 | $18,741.46 |
| 5 | $18,741.46 | $1,200.00 | $1,394.08 | $21,335.54 |
| 6 | $21,335.54 | $1,200.00 | $1,581.61 | $24,117.15 |
| 7 | $24,117.15 | $1,200.00 | $1,782.69 | $27,099.84 |
| 8 | $27,099.84 | $1,200.00 | $1,998.31 | $30,298.15 |
| 9 | $30,298.15 | $1,200.00 | $2,229.51 | $33,727.66 |
| 10 | $33,727.66 | $1,200.00 | $2,477.43 | $37,405.09 |
| 11 | $37,405.09 | $1,200.00 | $2,743.28 | $41,348.37 |
| 12 | $41,348.37 | $1,200.00 | $3,028.34 | $45,576.71 |
| 13 | $45,576.71 | $1,200.00 | $3,334.00 | $50,110.71 |
| 14 | $50,110.71 | $1,200.00 | $3,661.77 | $54,972.47 |
| 15 | $54,972.47 | $1,200.00 | $4,013.22 | $60,185.70 |
| 16 | $60,185.70 | $1,200.00 | $4,390.09 | $65,775.78 |
| 17 | $65,775.78 | $1,200.00 | $4,794.20 | $71,769.98 |
| 18 | $71,769.98 | $1,200.00 | $5,227.52 | $78,197.50 |
| 19 | $78,197.50 | $1,200.00 | $5,692.16 | $85,089.66 |
| 20 | $85,089.66 | $1,200.00 | $6,190.40 | $92,480.05 |
How It Works
Compound interest is calculated using the formula A = P(1 + r/n)nt, where P is the principal, r is
the annual interest rate, n is the number of compounding periods per year, and t is the
time in years. With regular contributions, each deposit also earns interest, dramatically
accelerating growth.
Compounding frequency matters: daily compounding yields slightly more than annual
compounding at the same stated rate. The effective annual yield (APY) is (1 + r/n)n − 1 and lets you compare products with
different compounding schedules on equal footing.
Rule of 72: divide 72 by your annual rate to estimate how many years it takes to double your money. At 6%, money doubles in roughly 12 years; at 9%, about 8 years.
The power of starting early: time is the most powerful factor in compound growth. Starting 10 years earlier can roughly double or triple your final balance, even with a lower monthly contribution.
Inflation and real returns: a nominal return of 7% with 3% inflation yields
a real return of roughly (1.07 / 1.03) − 1 ≈ 3.88%. The
"In today's dollars" figure shows what your future balance is worth in current purchasing
power — a more honest measure of actual wealth gained.