See what your money could grow into
Enter what you have today, what you'll add each month and a yearly return. You'll see your future balance, how much of it is pure growth, and why the years you give it matter more than anything else.
- Free, no sign-up
- Instant results
- Year-by-year breakdown
How it works
Four numbers, about 30 seconds
Compound interest just means your growth starts earning growth of its own. Here's what to type in.
- 1
Your starting amount
What you're investing today. Zero is fine if you're starting from scratch. - 2
What you'll add monthly
The amount you'll put in every month. Even $100 makes a visible difference over 20+ years. - 3
A yearly return
Your best guess at the average yearly return. Lots of long-term planners use 6 to 8% for a mostly-stock portfolio. Go lower to be careful. - 4
How many years
How long the money stays invested. Then read the results: the growth line, the totals and the year-by-year table.
Compound interest calculator
Results update as you type.
Money you're investing today.
What you'll add every month from now on.
An average you expect each year. It's an assumption, not a promise.
How long you'll leave the money alone.
How often growth gets added to your balance. Monthly is a fine default.
Future value
$691,150
You put in
$190,000
Growth earned
$501,150
Growth share of total
72.5%
| Frequency | Future value | Total growth | Difference vs. annual |
|---|---|---|---|
| Annually (1x/year) | $642,887 | $452,887 | -- |
| Quarterly (4x/year) | $681,836 | $491,836 | +$38,949 |
| Monthly (12x/year)(selected) | $691,150 | $501,150 | +$48,263 |
| Daily (365x/year) | $695,747 | $505,747 | +$52,860 |
| Year | Put in | Growth | Balance |
|---|---|---|---|
| 1 | $16,000 | $919 | $16,919 |
| 2 | $22,000 | $2,339 | $24,339 |
| 3 | $28,000 | $4,294 | $32,294 |
| 4 | $34,000 | $6,825 | $40,825 |
| 5 | $40,000 | $9,973 | $49,973 |
| 6 | $46,000 | $13,782 | $59,782 |
| 7 | $52,000 | $18,299 | $70,299 |
| 8 | $58,000 | $23,578 | $81,578 |
| 9 | $64,000 | $29,671 | $93,671 |
| 10 | $70,000 | $36,639 | $106,639 |
| 11 | $76,000 | $44,544 | $120,544 |
| 12 | $82,000 | $53,455 | $135,455 |
| 13 | $88,000 | $63,443 | $151,443 |
| 14 | $94,000 | $74,587 | $168,587 |
| 15 | $100,000 | $86,971 | $186,971 |
| 16 | $106,000 | $100,683 | $206,683 |
| 17 | $112,000 | $115,820 | $227,820 |
| 18 | $118,000 | $132,486 | $250,486 |
| 19 | $124,000 | $150,790 | $274,790 |
| 20 | $130,000 | $170,851 | $300,851 |
| 21 | $136,000 | $192,796 | $328,796 |
| 22 | $142,000 | $216,760 | $358,760 |
| 23 | $148,000 | $242,892 | $390,892 |
| 24 | $154,000 | $271,345 | $425,345 |
| 25 | $160,000 | $302,290 | $462,290 |
| 26 | $166,000 | $335,905 | $501,905 |
| 27 | $172,000 | $372,384 | $544,384 |
| 28 | $178,000 | $411,934 | $589,934 |
| 29 | $184,000 | $454,777 | $638,777 |
| 30 | $190,000 | $501,150 | $691,150 |
Your results, explained
How to read your results
Four numbers tell the whole story. Here's what each one means for you.
- Future value
- What the account could be worth at the end, if the return you picked held up on average.
- You put in
- Your starting amount plus every monthly contribution. This is your money, not growth.
- Growth earned
- Money your money made. Compare it to what you put in. Over long stretches it's often the bigger number.
- The shape of the chart
- The blue growth layer starts thin and gets thick in the later years. That's why starting five years sooner can beat adding more later.
This is an educational estimate, not financial advice. It assumes the same return every year, which real markets never deliver, and it doesn't include taxes, fees or inflation. Lower the return to allow for them.
Compound interest, explained
Compound interest is calculated using the formula:
- P = Initial principal (starting amount)
- r = Annual interest rate (as a decimal)
- n = Number of times interest compounds per year
- t = Number of years
- PMT = Periodic contribution amount
- FV = Future value
Simple interest is calculated only on the original principal amount. Compound interest is calculated on both the principal and the accumulated interest from previous periods. This creates an exponential growth effect that accelerates over time.
For example, $10,000 at 7% for 30 years earns $21,000 with simple interest (totaling $31,000) but grows to approximately $76,123 with annual compounding, more than double the simple interest result.
The Rule of 72 is a quick way to estimate how long it takes for an investment to double. Divide 72 by the annual interest rate to get the approximate number of years to double your money.
At a 6% annual return, your money doubles approximately every 12 years. At 8%, it doubles every 9 years. At 10%, every 7.2 years.
A dollar today is worth more than a dollar tomorrow because of its potential to earn interest. This fundamental financial concept means that investing earlier, even with smaller amounts, can lead to greater wealth than investing larger amounts later.
Starting just 10 years earlier with the same monthly contribution can result in significantly more wealth at retirement age, thanks to the extra years of growth on top of growth.
The more frequently interest compounds, the greater the total amount of interest earned. Daily compounding yields slightly more than monthly, which yields more than quarterly, which yields more than annually.
However, the difference between monthly and daily compounding is relatively small. The biggest jump in returns comes from moving from annual to quarterly or monthly compounding. Use the comparison table in the calculator to see the exact differences for your numbers.
Nominal returns are the raw percentage gains on your investment. Real returns account for inflation, giving you a clearer picture of your actual purchasing power growth.
If your investment earns 8% annually but inflation averages 3%, your real return is approximately 5%. When planning for long-term goals, using a real rate of return gives more accurate projections of future purchasing power.