Compound Interest Calculator
Project savings growth.
Your savings plan
Principal + contributions + rate + time
Final balance
$142,438
Contributed
$53,000
Interest earned
$89,438
Multiplier
2.69×
Year by year
| Year | Contrib. | Interest | Balance |
|---|---|---|---|
| 1 | 2,400 | 505 | $7,905 |
| 2 | 2,400 | 746 | $11,051 |
| 3 | 2,400 | 1,007 | $14,458 |
| 4 | 2,400 | 1,290 | $18,148 |
| 5 | 2,400 | 1,596 | $22,145 |
| 6 | 2,400 | 1,928 | $26,473 |
| 7 | 2,400 | 2,287 | $31,160 |
| 8 | 2,400 | 2,676 | $36,236 |
| 9 | 2,400 | 3,098 | $41,734 |
| 10 | 2,400 | 3,554 | $47,687 |
| 11 | 2,400 | 4,048 | $54,135 |
| 12 | 2,400 | 4,583 | $61,119 |
| 13 | 2,400 | 5,163 | $68,681 |
| 14 | 2,400 | 5,791 | $76,872 |
| 15 | 2,400 | 6,470 | $85,742 |
| 16 | 2,400 | 7,207 | $95,349 |
| 17 | 2,400 | 8,004 | $105,753 |
| 18 | 2,400 | 8,867 | $117,020 |
| 19 | 2,400 | 9,803 | $129,223 |
| 20 | 2,400 | 10,815 | $142,438 |
How this tool works
Compound interest is what Einstein called 'the eighth wonder of the world'. The difference from simple interest: each year, interest adds to the principal, and next year's interest is calculated on the new total. After 30 years at 8% annual, $10,000 turns into $100,627 — without adding a cent.
This calculator combines your initial deposit, monthly or yearly contributions, expected rate and time horizon. Returns final capital, total interest and a year-by-year breakdown so you see the exponential effect.
Formula
Final capital = P(1 + r/n)^(nt) + PMT × (((1 + r/n)^(nt) − 1) / (r/n)). P=principal, r=annual rate decimal, n=compounds per year, t=years, PMT=contribution per period.
Frequently asked questions
- Realistic annual rate?
- S&P 500 historical average: 7–10% nominal, ~5–7% real (after inflation). LATAM fixed income/CDs: 6–12% nominal, near 0% real in high-inflation.
- Monthly vs annual?
- Monthly always wins — more compounds per year = more interest on interest. The 30-year, 8% diff is ~3% more final capital.
- How does inflation factor in?
- By default we show nominal value. For real value, subtract expected inflation from the rate (e.g. 8% nominal − 4% inflation = 4% real).
- What if I stop contributing?
- Capital keeps growing on interest alone. Contributing 10 years then waiting 20 beats contributing 30 starting 10 years later.