Compound interest calculator
Enter a starting amount, how much you add regularly, the yearly rate and the number of years to see the final balance, how much of it is your own money and how much is interest, with a chart and a year-by-year table. You can choose how often interest is added, from yearly to continuous, and whether deposits land at the start or the end of each period. Or turn it around: see how long it takes to reach a goal, or what yearly rate a goal needs. It is an illustration with a steady rate, not advice. Everything is worked out in your browser and nothing you type is sent anywhere.
The nominal yearly rate, from 0 to 100.
A whole number from 1 to 100.
Leave empty to ignore inflation. If filled in, the page also shows the final balance in today's money.
Result
- Final balance
- $144,572.72
- Total you put in
- $58,000.00
- Total interest earned
- $86,572.72
- Effective yearly growth
- 7.23%
Growth chart
Bar chart of the balance at the end of each year, from $13,201.42 after year 1 to $144,572.72 after year 20. The lower part of each bar is what you put in, the upper part is interest.
Year by year
Amounts are rounded half up to the cent when shown. Interest per year is the change in the shown balance minus the money added that year, so each row adds up.
| Year | Added | Interest | Total put in | Balance |
|---|---|---|---|---|
| Year 1 | $2,400.00 | $801.42 | $12,400.00 | $13,201.42 |
| Year 2 | $2,400.00 | $1,032.85 | $14,800.00 | $16,634.27 |
| Year 3 | $2,400.00 | $1,281.01 | $17,200.00 | $20,315.28 |
| Year 4 | $2,400.00 | $1,547.11 | $19,600.00 | $24,262.39 |
| Year 5 | $2,400.00 | $1,832.44 | $22,000.00 | $28,494.83 |
| Year 6 | $2,400.00 | $2,138.41 | $24,400.00 | $33,033.24 |
| Year 7 | $2,400.00 | $2,466.50 | $26,800.00 | $37,899.74 |
| Year 8 | $2,400.00 | $2,818.29 | $29,200.00 | $43,118.03 |
| Year 9 | $2,400.00 | $3,195.52 | $31,600.00 | $48,713.55 |
| Year 10 | $2,400.00 | $3,600.03 | $34,000.00 | $54,713.58 |
| Year 11 | $2,400.00 | $4,033.76 | $36,400.00 | $61,147.34 |
| Year 12 | $2,400.00 | $4,498.86 | $38,800.00 | $68,046.20 |
| Year 13 | $2,400.00 | $4,997.59 | $41,200.00 | $75,443.79 |
| Year 14 | $2,400.00 | $5,532.35 | $43,600.00 | $83,376.14 |
| Year 15 | $2,400.00 | $6,105.79 | $46,000.00 | $91,881.93 |
| Year 16 | $2,400.00 | $6,720.67 | $48,400.00 | $101,002.60 |
| Year 17 | $2,400.00 | $7,380.00 | $50,800.00 | $110,782.60 |
| Year 18 | $2,400.00 | $8,087.00 | $53,200.00 | $121,269.60 |
| Year 19 | $2,400.00 | $8,845.10 | $55,600.00 | $132,514.70 |
| Year 20 | $2,400.00 | $9,658.02 | $58,000.00 | $144,572.72 |
How this is calculated
- •The yearly rate is the nominal rate you type. If interest is added n times a year, money grows by (1 + rate / n) to the power n over a year; with continuous compounding it grows by e to the power rate.
- •Inside the year, money is credited every month at the equivalent monthly rate, so after exactly one year it has grown by that same yearly factor. Real banks may credit on set dates, so their figures can differ by small amounts.
- •Contributions are paid at the start or the end of each month (or once a year). A payment at the start of a period earns interest for that whole period.
- •The balance is kept at 60 decimal digits with no rounding along the way, and rounded half up to the cent only when shown. No floating-point numbers are used.
- •Inflation, if you enter it, only divides the final figures by (1 + inflation) for each year to give a real, today's-money value. Contributions stay the same nominal amount each year. Taxes, fees and changing rates are not included.
An illustration, not advice
This calculator shows what a steady rate would do to the numbers you type. Real returns are not steady and are not guaranteed, and taxes and fees are left out. Use it to compare ideas, not as a forecast or as financial advice.
How it works
- •Pick the question: what the balance will be, how long it takes to reach a goal, or what yearly rate you would need.
- •Fill in the starting amount, the regular deposit and how often it is paid, the yearly rate and how often interest is added. Add a number of years, or a goal amount for the other two questions.
- •Read the final balance, the money you put in and the interest earned. Optionally add a yearly inflation rate to see the final balance in today's money too.
- •Check the chart and the year-by-year table to see when interest starts to do more of the work than your deposits.
Questions
- Does adding interest more often make a big difference?
- A small one. For 10,000 at 5% a year over 10 years, interest added yearly gives 16,288.95, quarterly 16,436.19, daily 16,486.65 and continuously 16,487.21. The gap between yearly and daily is 197.70; the gap between daily and continuous is only 0.56.
- Should deposits go in at the start or the end of the month?
- A deposit at the start of a period earns interest for that whole period, so it ends slightly higher. With 10,000 to start, 200 a month and 7% a year added monthly over 20 years, deposits at the end of each month give 144,572.72 and deposits at the start give 145,180.47, a difference of 607.75.
- Will this match my bank or fund exactly?
- Not necessarily. Here money is credited every month at the rate that makes a full year grow by exactly the yearly factor, and the balance is rounded to the cent only when shown. A bank may credit interest on fixed dates, round every credit, or use a different day count, so its figures can differ by small amounts. Check the terms of your own account.
- What does the inflation option do, and is this advice?
- If you enter a yearly inflation rate, the page divides the final balance by (1 + inflation) once for each year, giving a value in today's money; your deposits stay the same amount every year. With 2.5% inflation, the 144,572.72 above is worth 88,228.53 in today's money. Real returns are not steady and are not guaranteed, and taxes and fees are not included, so treat every figure as an illustration, not advice.