Compound Interest Calculator
Enter a starting amount, a monthly deposit, a yearly interest rate and a term, and see what the money grows to. You choose how often interest is added, from yearly to daily, and whether deposits are made at the start or the end of each month. The result shows the final balance, the interest earned, the money you put in and the effective annual rate, plus a year-by-year table. Everything runs in your browser. This is a calculator for information, not financial advice.
Year by year
| Year | Money in | Interest | Balance |
|---|---|---|---|
| 1 | 12,400.00 | 683.89 | 13,083.89 |
| 2 | 14,800.00 | 1,557.99 | 16,357.99 |
| 3 | 17,200.00 | 2,634.03 | 19,834.03 |
| 4 | 19,600.00 | 3,924.46 | 23,524.46 |
| 5 | 22,000.00 | 5,442.51 | 27,442.51 |
| 6 | 24,400.00 | 7,202.21 | 31,602.21 |
| 7 | 26,800.00 | 9,218.48 | 36,018.48 |
| 8 | 29,200.00 | 11,507.14 | 40,707.14 |
| 9 | 31,600.00 | 14,084.97 | 45,684.97 |
| 10 | 34,000.00 | 16,969.84 | 50,969.84 |
For information only, not financial advice. A real account may add interest, round or credit deposits on different dates, so check its terms. Interest is added at the frequency you chose and deposits are made at the start or end of each month, as selected. Taxes, fees and inflation are not included.
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Math & MoneyAbout the Compound Interest Calculator
The compound interest calculator adds interest to the balance on every compounding date, so that interest earns interest. Each period it multiplies the balance by 1 plus the yearly rate divided by the number of periods, and deposits are added at the end or at the start of each month. It uses fixed-point BigInt arithmetic with 60 decimal places and rounds the result half up to the cent only at the end, so there is no floating point drift, even after 100 years of daily compounding. The effective annual rate is (1 + r/n) to the power n, minus 1, which shows why 5% compounded monthly really grows 5.1162% a year. When interest and deposits fall on the same date, the interest is added first, so a deposit starts earning from the next date. Input is read strictly: amounts with up to 2 decimals, a rate from 0 to 100 percent with up to 4 decimals, and a term of 1 month to 100 years, and anything else is reported instead of guessed. The results were compared with Python's Fraction and Decimal types on 6,000 scenarios covering every compounding frequency, both deposit timings and terms up to 100 years, with no differences. Real accounts can differ, for example by adding interest on other dates or by using a day count, so treat the result as an estimate. This tool is for information only and is not financial advice. Everything runs in your browser and nothing is uploaded.
What is the compound interest formula?▾
For a single deposit, the balance is the starting amount times (1 + r/n) to the power n times t, where r is the yearly rate as a decimal, n is how many times a year interest is added and t is the number of years. For example, 10,000 at 5% compounded yearly for 10 years is 10,000 x 1.05^10, or 16,288.95.
Does compounding more often make a big difference?▾
A small one. 10,000 at 5% for 10 years gives 16,288.95 compounded yearly and 16,470.09 compounded monthly. The rate and the time matter far more than the frequency.
What is the effective annual rate?▾
It is the yearly growth you actually get after compounding. A rate of 5% compounded monthly has an effective annual rate of about 5.1162%, because each month's interest earns interest too. It is also called the annual percentage yield, APY.
Is this financial advice?▾
No. It is a calculator that does the arithmetic exactly for the settings you enter. Real accounts can add interest on other dates and charge fees or taxes, so check the terms of the account.
Is my data uploaded?▾
No. The calculation runs in your browser, and what you type is not sent anywhere or stored.