What is compound interest?
Interest earned on your money and on the interest it has already earned. Compounding is that interest being added to the balance.
Compound Interest Calculator
See how much your savings or investment will be worth, with monthly deposits, compounding from daily to yearly and a year-by-year table.
Initial deposit
$
Regular amount
DepositWithdraw
Monthly deposit
$
Interest rate
% a year
Years
Months
Compound
$47,
$10,000 plus $200 a month at 5% compounded monthly is $47,526.55 after 10 years.
Where the money comes from
- Initial deposit
- $10,000.00 · 21%
- Contributions
- $24,000.00 · 50%
- Interest earned
- $13,526.55 · 28%
Growth by year
- Initial deposit
- Contributions
- Interest
Working
10,000 × (1 + 0.05 ÷ 12)^(12 × 10) = 16,470.09
200 × ((1 + 0.05 ÷ 12)^120 − 1) ÷ (0.05 ÷ 12) = 31,056.46
16,470.09 + 31,056.46 = 47,526.55
Details
- APY (effective annual rate)
- 5.116%
- Doubling time, no deposits
- 13.9 years
- Rule of 72 estimate
- 14.4 years
- In today's money
- Add inflation in the settings
An estimate at a fixed rate. Real accounts can change their rate, round interest or charge fees, and investments can lose value.
Deposit every
MonthQuarterYear
Deposits go in
At the startAt the end
At the start, each deposit earns interest for its own period too.
Raise the deposit each year
%
For savings that grow with your pay.
Inflation
% a year
Shows the final balance in today's money too.
Currency
Year-by-year table
YearlyMonthly
| Year | Deposits | Interest | Total interest | Balance |
|---|---|---|---|---|
| 1 | $2,400.00 | $567.39 | $567.39 | $12,967.39 |
| 2 | $2,400.00 | $719.21 | $1,286.60 | $16,086.60 |
| 3 | $2,400.00 | $878.79 | $2,165.39 | $19,365.39 |
| 4 | $2,400.00 | $1,046.54 | $3,211.93 | $22,811.93 |
| 5 | $2,400.00 | $1,222.87 | $4,434.80 | $26,434.80 |
| 6 | $2,400.00 | $1,408.23 | $5,843.03 | $30,243.03 |
| 7 | $2,400.00 | $1,603.06 | $7,446.09 | $34,246.09 |
| 8 | $2,400.00 | $1,807.87 | $9,253.96 | $38,453.96 |
| 9 | $2,400.00 | $2,023.15 | $11,277.11 | $42,877.11 |
| 10 | $2,400.00 | $2,249.45 | $13,526.55 | $47,526.55 |
Change any number and the balance, the chart and the table update at once, so a higher rate or a bigger deposit is a quick test.
Free with no sign-up, and the amounts you type are worked out in your browser, never sent anywhere.
- Monthly contributions or withdrawals
- Daily, monthly or yearly compounding
- Year-by-year table for Excel
How to calculate compound interest
Type four numbers and the balance appears, with the working and every year laid out.
Enter your balance
Type your initial deposit, the yearly interest rate and how many years to grow it. Then pick how often it compounds.
Add monthly deposits
Put in what you add each month, or switch to Withdraw to take money out. More settings hold quarterly and yearly.
Read the yearly table
The chart and table show how much your savings grow each year. Copy the table into Excel or download it as a CSV.
Compound interest formula
The formula for compound interest is A = P(1 + r/n)^(nt). P is the amount you start with, r the yearly rate as a decimal, n how many times a year interest is added and t the number of years. A is the future value; A minus P is the interest. For the monthly compound interest formula, n is 12.
As a compound interest example, 10,000 at 5% compounded monthly for 10 years is 10,000 × (1 + 0.05 ÷ 12)^120 = 16,470.09. Adding 200 at the end of every month puts in 24,000 more, and those deposits grow to 31,056.46, so the account ends on 47,526.55.
The compound interest with monthly contributions formula adds PMT × ((1 + i)^N − 1) ÷ i, where i is the monthly rate and N the number of deposits. Interest compounded continuously turns the first formula into A = Pe^(rt). The Working block shows each part with your numbers.
Compounded daily, monthly or annually
The more often interest is added, the sooner it starts earning interest of its own. At 5% a year, 10,000 left for 10 years grows to 16,288.95 compounded annually, 16,436.19 quarterly, 16,470.09 monthly and 16,486.65 when it is compounded daily.
Banks compare these with APY, the annual percentage yield, also called the effective annual rate. A 5% rate compounded daily pays 5.127% over a year, and monthly pays 5.116%. A savings account that quotes its APY has already counted the compounding in.
Compounded daily means the yearly rate is split into 365 parts, and one part is added each day. Interest compounded continuously is the limit, yet at 5% it adds only 0.56 more than daily over 10 years. Pick Daily in the Compound box to try it with your figures.
Compound interest vs simple interest
Simple interest is paid on the starting amount only, so its formula is just P × r × t. Compound interest is paid on the starting amount plus the interest already earned, so each year's interest is a little bigger than the one before: the power of compounding.
The difference between simple and compound interest grows with time. 10,000 at 6% simple interest for 30 years earns 18,000 and ends at 28,000. Compounded once a year, it ends at 57,434.91, more than twice as much from the very same rate.
The same maths works against you on debt: an unpaid credit card balance compounds too. In the calculator's chart, watch the interest band on top of each bar; with long enough terms it grows taller than everything you paid in.
A savings and investment growth calculator
Monthly contributions
Add a deposit each month, quarter or year. For increasing contributions, raise it a percent a year.
Compounding frequency
Daily, monthly, quarterly, twice a year, yearly or continuous, with the APY shown for each choice.
Regular withdrawals
Take a set amount out each month to see how long your savings will last and the month they run out.
Adjust for inflation
Add an inflation rate to see the final balance in today's money as well as the number on paper.
Compound interest graph
A stacked chart splits each year into what you paid in and the interest, with a full yearly table.
Copy to Excel or CSV
Paste the table straight into Excel or Sheets, or save a CSV. Pick dollars, pounds, euros or rupees.
Your money figures stay private
Every sum runs in this tab. Nothing you type is sent, saved or tied to you.
Processing
The balance, chart and table are worked out by your browser. No amount or rate goes to a server.
Storage
Nothing is saved. Reload the page and the boxes go back to the example figures, with no history.
Account
Use this free compound interest calculator as often as you like, without an account or an email.
Questions about compound interest
How does compound interest work?
Each period, interest is added to the balance, and the next interest is worked out on that larger total, so the growth speeds up.
What is the rule of 72?
Divide 72 by the yearly rate to guess how many years money takes to double. At 6% that gives 12; the exact doubling time is 11.9.
How do you calculate APY?
Use (1 + r/n)^n − 1, with r the rate as a decimal and n the times a year interest is added. 5% compounded monthly is a 5.116% APY.
How do I calculate compound interest in Excel?
Type =FV(5%/12, 10*12, -200, -10000) for 10,000 plus 200 a month at 5% for 10 years. It returns 47,526.55, as this page does.
What does compounded annually mean?
Interest is added once a year, on the balance on that date. 1,000 at 5% becomes 1,050 after one year and 1,102.50 after two.
How does compound interest work with stocks?
Shares pay no interest, but reinvested dividends and rising prices compound the same way. Returns vary, so use an average rate.
How is interest calculated on a savings account?
Most banks work out interest on each day's balance and add it monthly. 5,000 at 4.5% compounded monthly earns 229.70 in a year.
Still stuck, or found a problem? Email dobliquestudio@gmail.com and we will help.