// INVESTING
Compound Interest
Calculator
See how your money grows through the power of compounding. Model a lump sum and regular contributions over any time horizon, with inflation adjustment.
// INVESTMENT_SETUP
Starting amount and contributions
Initial lump sum$10,000
Regular contribution$500
Contribution frequency
// RETURNS & HORIZON
Rate of return and time period
Annual return rate8.0%
Compounding frequency
Time horizon20 years
Inflation rate (for real value)2.5%
Final balance after 20 years
$343.8k
$209.8k in today's dollars · $130,000 contributed · $213.8k interest earned
Total contributed
$130.0k
38% of final balance
Interest earned
$213.8k
62% of final balance
Rule of 72 (doubling)
9.0 yrs
At 8% per year
// GROWTH_BREAKDOWN
Contributions: $130.0kInterest: $213.8k
38% contributions62% compound interest
You put in $130,000 over 20 years. Compound interest adds another $213.8k — making 164% of your final balance pure interest growth. Regular contributions of $500/month add $6.0k/year.
// YEAR_BY_YEAR_GROWTH
Sampled key years · Real balance is inflation-adjusted
| Year | Contributions | Interest earned | Balance | Real balance |
|---|---|---|---|---|
| 1 | $10.0k | $7.1k | $17.1k | $16.6k |
| 2 | $16.0k | $8.7k | $24.7k | $23.5k |
| 3 | $22.0k | $11.0k | $33.0k | $30.6k |
| 4 | $28.0k | $13.9k | $41.9k | $38.0k |
| 5 | $34.0k | $17.6k | $51.6k | $45.6k |
| 6 | $40.0k | $22.1k | $62.1k | $53.6k |
| 7 | $46.0k | $27.5k | $73.5k | $61.9k |
| 8 | $52.0k | $33.9k | $85.9k | $70.5k |
| 9 | $58.0k | $41.2k | $99.2k | $79.4k |
| 10 | $64.0k | $49.7k | $113.7k | $88.8k |
| 11 | $70.0k | $59.3k | $129.3k | $98.6k |
| 12 | $76.0k | $70.3k | $146.3k | $108.8k |
| 13 | $82.0k | $82.7k | $164.7k | $119.4k |
| 14 | $88.0k | $96.5k | $184.5k | $130.6k |
| 15 | $94.0k | $112.1k | $206.1k | $142.3k |
| 16 | $100.0k | $129.4k | $229.4k | $154.5k |
| 17 | $106.0k | $148.7k | $254.7k | $167.4k |
| 18 | $112.0k | $170.0k | $282.0k | $180.8k |
| 19 | $118.0k | $193.7k | $311.7k | $195.0k |
| 20 | $124.0k | $219.8k | $343.8k | $209.8k |
General information only. Returns are assumed constant — real markets fluctuate significantly year to year. This model does not account for tax on investment income, inflation's effect on contributions, or fund fees. The "real balance" column adjusts for inflation at 2.5% annually. Past returns do not predict future performance. Not financial advice.