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Compound Interest Calculator

See how savings grow with compound interest and regular deposits, year by year.

$
%
years
$

Result

Balance after 20 years
$4,926.80
Total deposits
$1,000.00
Total interest earned
$3,926.80
Effective annual rate (APY)
8.3%
Deposits vs interest over timeDepositsInterest
Year 1: Deposits $1,000.00, Interest $83.001Year 2: Deposits $1,000.00, Interest $172.89Year 3: Deposits $1,000.00, Interest $270.243Year 4: Deposits $1,000.00, Interest $375.67Year 5: Deposits $1,000.00, Interest $489.855Year 6: Deposits $1,000.00, Interest $613.50Year 7: Deposits $1,000.00, Interest $747.427Year 8: Deposits $1,000.00, Interest $892.46Year 9: Deposits $1,000.00, Interest $1,049.539Year 10: Deposits $1,000.00, Interest $1,219.64Year 11: Deposits $1,000.00, Interest $1,403.8711Year 12: Deposits $1,000.00, Interest $1,603.39Year 13: Deposits $1,000.00, Interest $1,819.4713Year 14: Deposits $1,000.00, Interest $2,053.48Year 15: Deposits $1,000.00, Interest $2,306.9215Year 16: Deposits $1,000.00, Interest $2,581.39Year 17: Deposits $1,000.00, Interest $2,878.6517Year 18: Deposits $1,000.00, Interest $3,200.57Year 19: Deposits $1,000.00, Interest $3,549.2219Year 20: Deposits $1,000.00, Interest $3,926.80
Balance by year
YearTotal depositsTotal interestBalance
1$1,000.00$83.00$1,083.00
2$1,000.00$172.89$1,172.89
3$1,000.00$270.24$1,270.24
4$1,000.00$375.67$1,375.67
5$1,000.00$489.85$1,489.85
6$1,000.00$613.50$1,613.50
7$1,000.00$747.42$1,747.42
8$1,000.00$892.46$1,892.46
9$1,000.00$1,049.53$2,049.53
10$1,000.00$1,219.64$2,219.64
11$1,000.00$1,403.87$2,403.87
12$1,000.00$1,603.39$2,603.39
13$1,000.00$1,819.47$2,819.47
14$1,000.00$2,053.48$3,053.48
15$1,000.00$2,306.92$3,306.92
16$1,000.00$2,581.39$3,581.39
17$1,000.00$2,878.65$3,878.65
18$1,000.00$3,200.57$4,200.57
19$1,000.00$3,549.22$4,549.22
20$1,000.00$3,926.80$4,926.80

Compound interest is interest earned on your interest. Each period, the interest is added to the balance, so the next period’s interest is calculated on a larger amount. Over long periods this snowball effect is what makes saving and investing early so powerful.

How to use the compound interest calculator

  1. Enter your starting balance and the annual interest rate.
  2. Set how many years you plan to save and how often interest compounds.
  3. Optionally add a regular deposit, such as a monthly contribution.
  4. Read the final balance, then check the year-by-year table and chart.

Formula

A = P × (1 + r/n)^(n·t)

A is the final balance, P the initial balance, r the annual rate as a decimal, n the number of compounding periods per year and t the number of years.

With continuous compounding the formula becomes A = P × e^(r·t). Regular deposits are added at the end of each deposit period and then compound along with the rest of the balance.

Worked example

$1,000 at 8% compounded monthly for 20 years: A = 1000 × (1 + 0.08/12)^(240) ≈ $4,926.80. You deposited $1,000, so $3,926.80 is interest.

The rule of 72

A quick way to estimate doubling time: divide 72 by the annual rate. At 8%, money doubles in roughly 72 ÷ 8 = 9 years.

Frequently asked questions

What is the difference between simple and compound interest?

Simple interest is paid only on the original amount. Compound interest is also paid on interest already earned, so the balance grows faster over time.

Does compounding frequency matter much?

More frequent compounding gives a slightly higher return. At 8%, yearly compounding gives an effective 8% while monthly gives about 8.30%. The jump from daily to continuous is tiny.

Are the results guaranteed?

No. The calculator assumes a constant rate. Real investment returns vary, and taxes and fees reduce growth.

Last updated · Calculations checked by automated tests· Editorial policy

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