Finance
Compound Interest & FI Calculator
Project how your savings grow with compounding, or find out exactly when you'll hit financial independence — both with a chart of your balance over time.
Starting point
Assumptions
Result
Balance after 20 years
$300,851
You'll have contributed $130,000 — compounding adds another $170,851 on top of that.
- Total contributed
- $130,000
- Growth from compounding
- $170,851
- Share of the balance that's growth
- 57%
A planning estimate, not a guarantee — real markets don't return a steady rate every year.
How it grows
| Year | Balance | Contributed | Growth |
|---|---|---|---|
| 0 | $10,000 | $10,000 | $0 |
| 1 | $16,919 | $16,000 | $919 |
| 2 | $24,339 | $22,000 | $2,339 |
| 3 | $32,294 | $28,000 | $4,294 |
| 4 | $40,825 | $34,000 | $6,825 |
| 5 | $49,973 | $40,000 | $9,973 |
| 6 | $59,782 | $46,000 | $13,782 |
| 7 | $70,299 | $52,000 | $18,299 |
| 8 | $81,578 | $58,000 | $23,578 |
| 9 | $93,671 | $64,000 | $29,671 |
| 10 | $106,639 | $70,000 | $36,639 |
| 11 | $120,544 | $76,000 | $44,544 |
| 12 | $135,455 | $82,000 | $53,455 |
| 13 | $151,443 | $88,000 | $63,443 |
| 14 | $168,587 | $94,000 | $74,587 |
| 15 | $186,971 | $100,000 | $86,971 |
| 16 | $206,683 | $106,000 | $100,683 |
| 17 | $227,820 | $112,000 | $115,820 |
| 18 | $250,486 | $118,000 | $132,486 |
| 19 | $274,790 | $124,000 | $150,790 |
| 20 | $300,851 | $130,000 | $170,851 |
How this works
Both calculators simulate your balance month by month, compounding your expected return and adding your contribution each month. The Compound Interest tab runs that simulation for a fixed number of years, so you can see how a given savings plan grows. The Financial Independence tab works backward from your desired annual spending and safe withdrawal rate to find your FI number — the portfolio you'd need to live off indefinitely — then runs the same simulation until your balance crosses it, showing how many years away that milestone actually is at your current pace. Both charts plot your balance and total contributions side by side, so you can see how much of the growth is compounding versus your own deposits.
FAQ
- What's the difference between the two calculators?
- Compound Interest projects your balance forward over a fixed number of years — useful for "how much will I have in 20 years?" Financial Independence works backward from your desired annual spending to find your FI number, then tells you how many years it takes to get there at your current savings rate. Switch between them with the tabs above; both share your starting savings, contribution, and return rate.
- What's a "financial independence number"?
- The portfolio size where your investments alone can cover your living expenses forever, without a job. It's your desired annual spending divided by your safe withdrawal rate — spend $40,000/year at a 4% withdrawal rate, and your FI number is $1,000,000.
- Why does this ask for a real (inflation-adjusted) return?
- Working in real terms means every number here — your savings, your spending goal, the projection — is expressed in today's purchasing power, so you're not separately guessing at decades of future inflation. If you'd rather use a nominal return, also increase your spending goal each year by your assumed inflation rate to keep the comparison fair.
- How is the year-by-year table and chart calculated?
- Both compound monthly: each month your balance grows by (annual return ÷ 12), then that month's contribution is added. The chart plots your balance and total contributions year by year; in FI mode it also marks your target and the year you cross it. The table stops at your chosen horizon (Compound Interest) or once you reach your FI number, up to 40 years (Financial Independence).
- What doesn't this calculator account for?
- Real markets don't return a steady percentage every year — sequence-of-returns risk means a bad stretch early on can matter more than the long-run average. It also doesn't factor in taxes, Social Security or pension income, or a spending goal that changes over time. Treat the result as a directional estimate, not a guarantee.