Compound Interest Calculator
See how a starting amount and regular monthly contributions grow with daily, monthly, quarterly or annual compounding — including fees and inflation.
Published by GrowThenDraw Editorial Team · Editorial policy · Methodology & sources
To reach $500,000 under these assumptions, start around $812/month.
Compound growth is before tax. Model local accounts and withdrawal tax in the United States investment calculator.
| Year | Total contributed | Compound growth | Balance | Today's money |
|---|---|---|---|---|
| 1 | $16,000 | $852 | $16,852 | $16,441 |
| 2 | $22,120 | $2,166 | $24,286 | $23,116 |
| 3 | $28,362 | $3,982 | $32,344 | $30,035 |
| 4 | $34,730 | $6,341 | $41,071 | $37,208 |
| 5 | $41,224 | $9,289 | $50,513 | $44,646 |
| 6 | $47,849 | $12,873 | $60,721 | $52,360 |
| 7 | $54,606 | $17,144 | $71,750 | $60,361 |
| 8 | $61,498 | $22,159 | $83,656 | $68,661 |
| 9 | $68,528 | $27,974 | $96,502 | $77,272 |
| 10 | $75,698 | $34,655 | $110,353 | $86,208 |
| 11 | $83,012 | $42,267 | $125,280 | $95,481 |
| 12 | $90,473 | $50,884 | $141,356 | $105,106 |
| 13 | $98,082 | $60,582 | $158,664 | $115,098 |
| 14 | $105,844 | $71,443 | $177,287 | $125,471 |
| 15 | $113,761 | $83,556 | $197,317 | $136,241 |
| 16 | $121,836 | $97,016 | $218,852 | $147,424 |
| 17 | $130,072 | $111,923 | $241,995 | $159,038 |
| 18 | $138,474 | $128,385 | $266,859 | $171,101 |
| 19 | $147,043 | $146,517 | $293,560 | $183,630 |
| 20 | $155,784 | $166,442 | $322,226 | $196,645 |
What this compound interest calculator shows
Enter a starting balance, a monthly contribution, the nominal annual rate and the number of years. The calculator separates the final value into money you contributed and compound growth. You can increase contributions each year, compare beginning-of-month with end-of-month deposits, and see the result in a currency that is familiar to you.
The target line solves the same calculation in reverse: it estimates the starting monthly contribution needed to reach your chosen goal under the displayed assumptions. It is a mathematical target, not a promise that an investment or savings account will deliver the rate entered.
How the compound interest formula works
For a single lump sum, the standard formula is A = P(1 + r/n)^(nt), where P is the starting principal, r is the nominal annual rate, n is the number of compounding periods per year and t is time in years. More frequent compounding produces a higher effective annual rate when the same nominal rate is used.
Regular monthly deposits do not all earn interest for the same length of time. This calculator processes each deposit separately using the equivalent monthly rate implied by your selected compounding frequency. A beginning-of-month deposit receives one extra month of growth compared with an end-of-month deposit.
Fees and inflation change the useful answer
A headline future value can be misleading. The fee input reduces the nominal growth rate and the calculator separately shows the estimated value lost to that fee. The inflation-adjusted result expresses the future balance in today's purchasing power using the inflation rate you enter.
Neither rate is a forecast. Try conservative, middle and optimistic cases. A small change in return, fees or time can create a large difference because each year's growth also earns future growth.
From a global estimate to a country-specific plan
Compound interest is the universal starting point, but real investing also involves account rules and tax. After running the simple projection, follow the country link beside the results to use GrowThenDraw's localized tools for the United States, United Kingdom, Australia, Canada, Singapore or Malaysia.
Frequently asked questions
What is compound interest?
Compound interest is growth earned on both the original principal and growth already added. Over long periods, earning growth on earlier growth is what creates the compounding effect.
Is daily compounding always better than monthly compounding?
At the same nominal annual rate, more frequent compounding produces a slightly higher effective annual rate. The difference is often much smaller than the effects of the quoted rate, regular contributions, fees and time.
When should monthly contributions be added?
Choose beginning of month when deposits are made before that month's growth is credited, or end of month when they are made afterward. Beginning-of-month contributions finish slightly higher because every deposit receives one extra month of growth.
What does inflation-adjusted value mean?
It converts the projected future balance into today's purchasing power using your inflation assumption. It helps compare a large future number with what that amount may actually buy.
How does the calculator estimate fee impact?
The entered annual fee is subtracted from the nominal annual rate. The calculator also runs the same contributions without that fee; the difference between the two ending balances is shown as estimated fee drag.
Does this calculator include tax?
No. Tax depends on country, account type and personal circumstances. Use the country-specific link beside the results for localized account and tax modelling.
Formula reference: Investor.gov compound interest calculator. Educational projection only, not savings, investment, tax or financial advice.