Calculateos

Compound Interest Calculator

Fill in a few simple fields and see how your money grows.

Used for every amount and result on this page.
The money you start with today.
Money you add on a regular schedule. Use a minus value for withdrawals.
The annual return you expect to earn.
Times per year that interest is added to your balance.
How long your money stays invested.
Advanced optionsOptional

Turn on to fine-tune with inflation, taxes, fees, and more.

Future balance

$19,318

in 10 yr
Deposited vs interest
$13,000Deposited
$6,318InterestInterest is what your money earns on top of what you put in. With compound interest, you also earn interest on the interest already added — so it grows faster over time.

Results are shown in future dollars (not adjusted for inflation).

Estimate only — not financial advice.

Deposits vs interest

The green band is interest earned above your deposits. Hover any point for details.

DepositedInterest

Balance breakdown

Interest earned each period plus running totals; advanced options (inflation, rate range, tax, fees, timing) are reflected here.

YearInvestedThis periodTotal interestBalance
1$2,200$112$112$2,312
2$3,400$206$318$3,718
3$4,600$308$626$5,226
4$5,800$417$1,043$6,843
5$7,000$534$1,577$8,577
6$8,200$659$2,236$10,436
7$9,400$794$3,030$12,430
8$10,600$938$3,968$14,568
9$11,800$1,092$5,060$16,860
10$13,000$1,258$6,318$19,318

How compound interest works

Interest is what your money earns for staying invested. With simple interest, you earn a return only on your starting amount. Compound interest works differently: each period's earnings are added to your balance, so the next period you earn on a larger sum. That snowball effect — earning returns on your returns — is why starting early and compounding often make such a big difference over time.

The formula behind it

Two parts add together: the growth of your initial amount, plus the growth of your regular contributions.

Initial amountA = P × (1 + r/n) ^ (n·t)
Contributions+ PMT × [ ((1 + r/n) ^ (n·t) − 1) ÷ (r/n) ]
P
initial amount
PMT
regular contribution
r
annual rate (as a decimal)
n
compounding times per year
t
number of years
How the advanced options change it

Contribution timing — start-of-period deposits multiply the contributions part by (1 + r/n).

Annual increase — PMT grows by your chosen % every year.

Tax & fee — trimmed from each period's interest and return.

Inflation — the final balance is divided by (1 + i) ^ t to show today's money.

Rate range — the whole formula is re-run at your rate ± the variance for the low/high band.

Your numbers, plugged in

Your inputsP = 1,000 · PMT = 100/mo · r = 0.07 · n = 12 · t = 10
Initial amount grows to$2,010
1,000 × (1 + 0.07/12) ^ 120
Contributions grow to$17,308
100 × [ ((1 + 0.07/12) ^ 120 − 1) ÷ (0.07/12) ]
Total future balance$19,318
2,009.66 + 17,308.48

What each field means

Initial amount
The money you start with — your principal.
Regular contribution
What you add each period; a minus value models withdrawals.
Annual interest rate
The annual rate of return you expect to earn.
Compound frequency
How often interest is added (monthly = 12x a year). Compounding more often earns a little more.
Length of time
How many years your money keeps growing.
Advanced options
Fine-tune the result: today's money (inflation), a range of rates, rising deposits, and the drag from tax and fees.
My wealth has come from a combination of living in America, some lucky genes, and compound interest.
— Warren Buffett
Investing is not about a once-in-a-lifetime opportunity. It is a life-long journey of prudent investments that grow with time. You need to start small and let the magic of compounding do its trick.
— Naved Abdali

Further reading

Compound interestWikipediaU.S. inflation rate (CPI)U.S. Bureau of Labor StatisticsWhat is Compound Interest?WealthsimpleWhat is compounding?Investopedia

Frequently asked questions

What's the difference between simple and compound interest?

Simple interest is earned only on your starting amount. Compound interest is also earned on the interest you have already accumulated, so your balance grows faster.

How often should interest compound?

More frequent compounding (daily or monthly) earns slightly more than annual compounding at the same yearly rate.

Can I model regular withdrawals?

Yes — enter a negative regular contribution to model money you take out each period.

Are the results inflation-adjusted?

By default, results are in future dollars. Turn on the inflation option to also see the value in today's money.

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