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Compound interest calculator

How savings grow with compound interest and regular contributions: daily to continuous compounding, a year-by-year table, a growth chart and inflation.

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Nominal yearly rate or expected return.

Your savings

Final balance $144,572.72, interest earned $86,572.72.

Balance after 20 years
$144,572.72
Total paid in
$58,000.00
Interest earned
$86,572.72
Effective annual rate
7.229%
APY with this compounding
Growth by year
13579111315171920
  • Money paid in
  • Interest earned
  • Top of the last bar: $144,573
Contributions and inflation
Contribute
Paid in at the

Shows the final balance in today's money.

Year by year

Balance year by year
YearPaid inInterestBalance
1$2,400.00$801.42$13,201.42
2$2,400.00$1,032.85$16,634.27
3$2,400.00$1,281.01$20,315.28
4$2,400.00$1,547.11$24,262.39
5$2,400.00$1,832.45$28,494.83
6$2,400.00$2,138.41$33,033.24
7$2,400.00$2,466.49$37,899.74
8$2,400.00$2,818.29$43,118.03
9$2,400.00$3,195.52$48,713.55
10$2,400.00$3,600.02$54,713.58
11$2,400.00$4,033.77$61,147.34
12$2,400.00$4,498.86$68,046.20
13$2,400.00$4,997.58$75,443.79
14$2,400.00$5,532.35$83,376.14
15$2,400.00$6,105.79$91,881.93
16$2,400.00$6,720.67$101,002.60
17$2,400.00$7,380.00$110,782.60
18$2,400.00$8,087.00$121,269.60
19$2,400.00$8,845.11$132,514.70
20$2,400.00$9,658.02$144,572.72

The rate is assumed to stay the same every year and nothing is rounded until display; real accounts round interest to the cent, and investments rise and fall. Taxes and fees are not included. This is an estimate to help you plan, not financial advice: lenders, card issuers and investments set their own terms, fees and rounding. Everything is calculated in your browser; nothing you type is sent anywhere.

How it works

This compound interest calculator shows how money grows when the interest earns interest too. Enter a starting amount, a monthly or yearly contribution, the interest rate and the number of years, and choose how often interest is compounded, from daily to continuously. With the defaults, $10,000 plus $200 a month at 7% compounded monthly grows to $144,572.72 in 20 years, of which $86,572.72 is interest.

The result comes with a year-by-year table (what you paid in, the interest earned and the balance), a chart of the growth and a CSV download. Add an inflation rate to see what the final balance is worth in today’s money.

Use it for a savings account, a certificate of deposit, or a rough projection of an investment with a steady return. Every figure here is an estimate to help you plan, not financial advice: lenders, card issuers and investments set their own terms, fees and rounding.

The compound interest formula

A single deposit P at a yearly rate R, compounded m times a year for t years, grows to A = P × (1 + R/m)^(m·t); compounded continuously, A = P × e^(R·t). For $10,000 at 5% for 10 years that is $16,288.95 compounded yearly, $16,470.09 monthly and $16,487.21 continuously.

Regular contributions C made p times a year are added period by period with the equivalent rate g = (1 + R/m)^(m/p) − 1: at the end of each period B ← B × (1 + g) + C, or at the start B ← (B + C) × (1 + g). This matches the closed formula FV = P(1 + g)^N + C × ((1 + g)^N − 1) ÷ g and works for any mix of contribution and compounding frequency. Nothing is rounded until the result is shown.

The effective annual rate (APY) is (1 + R/m)^m − 1: 5% compounded monthly is an APY of 5.116%. The inflation-adjusted value divides the balance by (1 + inflation)^t.

What $10,000 grows to

A one-off $10,000 with no further contributions, compounded monthly:

$10,000 after 10, 20 and 30 years by interest rate, compounded monthly (USD)
Rate10 years20 years30 years
3%$13,494$18,208$24,568
4%$14,908$22,226$33,135
5%$16,470$27,126$44,677
6%$18,194$33,102$60,226
7%$20,097$40,387$81,165
8%$22,196$49,268$109,357
10%$27,070$73,281$198,374

Monthly contributions over 30 years

Starting from zero and adding the same amount at the end of every month, 7% a year compounded monthly:

Balance after 30 years of monthly contributions at 7% (USD)
Each monthPaid inInterest earnedBalance after 30 years
$100$36,000$85,997$121,997
$250$90,000$214,993$304,993
$500$180,000$429,985$609,985
$1,000$360,000$859,971$1,219,971
$2,000$720,000$1,719,942$2,439,942

Does the compounding frequency matter?

Less than people expect. $10,000 at 6% for 10 years:

$10,000 at 6% for 10 years by compounding frequency (USD)
CompoundingBalanceEffective annual rate
Annually$17,908.486.000%
Quarterly$18,140.186.136%
Monthly$18,193.976.168%
Daily$18,220.296.183%
Continuously$18,221.196.184%

The rate and the time you leave the money invested matter far more than how often the interest is added.

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How to use it

  1. Enter the starting amount, the yearly interest rate (or expected return) and the number of years.
  2. Enter how much you add each month or year, and whether you add it at the start or the end of each period.
  3. Choose the compounding: daily, monthly, quarterly, yearly or continuous (check your account’s terms).
  4. Read the final balance, the interest earned and the table; add inflation to see the value in today’s money.

Frequently asked questions

How do I calculate compound interest?

For a single deposit: A = P × (1 + R/m)^(m·t), where P is the deposit, R the yearly rate as a decimal, m the compounding periods a year and t the years. $10,000 at 5% compounded yearly for 10 years is 10,000 × 1.05^10 = $16,288.95. With regular contributions the calculator adds each deposit period by period.

What is the difference between compound and simple interest?

Simple interest is paid only on the original amount; compound interest is also paid on the interest already earned. $10,000 at 5% for 30 years earns $15,000 of simple interest but $33,219.42 compounded yearly.

Is daily compounding much better than monthly?

Only slightly. At 6%, daily compounding gives an effective rate of 6.183% against 6.168% monthly: on $10,000 over 10 years the difference is under $30. Compare accounts by their APY, which already includes the compounding.

Does it matter if I contribute at the start or end of the month?

A little: money added at the start of each period earns one extra period of interest. Over 30 years of $500 a month at 7%, contributing at the start adds about 0.6% to the final balance.

What does the inflation-adjusted value mean?

What the final balance would buy in today’s prices. At 2.5% inflation, $100,000 in 20 years buys what about $61,000 buys today. Enter an inflation rate to see it for your own result.

What rate should I use for investments?

Stock and bond returns are not fixed. Long-run averages are often quoted around 5% to 7% a year after inflation for diversified stock funds, but any year can be far above or below. Use a cautious rate and treat the result as a projection, not a promise.

What is the rule of 72?

A shortcut for the doubling time: 72 ÷ the yearly rate. At 6% money doubles in about 12 years (the exact figure is 11.9 years compounded yearly).

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