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What is my monthly interest?

Enter your balance, the yearly interest rate and how often it compounds. See the monthly interest, month by month, and the total.

Your numbers

The rate your bank quotes, not the APY.
Compounding
Interest in the first month
$41.67

At 5% a year, $10,000.00 earns $41.67 of interest in the first month and $511.62 over the whole time.

Total interest
$511.62
Average interest a month
$42.63
Interest in the last month
$43.62
Ending balance
$10,511.62
Money put in
$10,000.00
Monthly rate
0.416667%
APY
5.1162%
Months
12

Interest in the first month: $41.67. At 5% a year, $10,000.00 earns $41.67 of interest in the first month and $511.62 over the whole time.

How much interest does each month earn?

What does each month look like?

The results are estimates for information only. They are not financial, tax, or legal advice. Check the numbers with your lender or a qualified professional before you decide. Terms of use

How to calculate

Computes the interest a savings balance earns each month and in total, at a yearly rate compounded daily, monthly, quarterly, twice a year or yearly, with an optional monthly deposit.

Example with the default inputs (Balance $10,000.00, Interest rate (yearly) 5%, Compounding Monthly, Added each month $0.00, Number of months 12): At 5% a year, $10,000.00 earns $41.67 of interest in the first month and $511.62 over the whole time.

Method: Each month, interest = balance × ((1 + r/m)^(m/12) − 1), where r is the yearly rate and m the compoundings a year; then the deposit is added.

  • The rate does not change.
  • Deposits are added at the end of each month.
  • With daily, quarterly, twice-yearly or yearly compounding, interest builds at the equivalent monthly rate, so the balance matches P(1 + r/m)^(mt) at every compounding date.
  • Tax and fees are not included.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Balance $10,000.00, Interest rate (yearly) 5%, Compounding Monthly, Number of months 12 gives Interest in the first month $41.67, Total interest $511.62, Ending balance $10,511.62, APY 5.11619%, Interest in the last month $43.62.Source: SEC Investor.gov compound interest formula A = P(1 + r/n)^(nt) (https://www.investor.gov/financial-tools-calculators/calculators/compound-interest-calculator)
  2. Balance $25,000.00, Interest rate (yearly) 4%, Compounding Daily, Number of months 12 gives Interest in the first month $83.47, Total interest $1,020.21, APY 4.080849%.Source: SEC Investor.gov compound interest formula with daily compounding (https://www.investor.gov/financial-tools-calculators/calculators/compound-interest-calculator)
  3. Balance $0.00, Interest rate (yearly) 6%, Compounding Monthly, Added each month $100.00, Number of months 12 gives Interest in the first month $0.00, Ending balance $1,233.56, Total interest $33.56, Money put in $1,200.00, Average interest a month $2.80.Source: Future value of an annuity (Microsoft Excel FV function, https://support.microsoft.com/en-us/office/fv-function-2eef9f44-a084-4c61-bdd8-4fe4bb1b71b3)
  4. Balance $10,000.00, Interest rate (yearly) 6%, Compounding Yearly, Number of months 24 gives Ending balance $11,236.00, Total interest $1,236.00.Source: SEC Investor.gov compound interest formula with yearly compounding (https://www.investor.gov/financial-tools-calculators/calculators/compound-interest-calculator)

How the monthly interest is worked out

Monthly rate. With a nominal yearly rate r (as a decimal) compounded m times a year (365, 12, 4, 2 or 1), the balance grows each month by

monthly rate = (1 + r ÷ m)^(m ÷ 12) − 1

So with monthly compounding the monthly rate is r ÷ 12, and with any compounding the balance matches P × (1 + r ÷ m)^(m × t) at every compounding date.

Month by month. Starting from the balance, for each month:

  1. Interest = balance × monthly rate.
  2. New balance = balance + interest + the monthly deposit (added at the end of the month; an empty deposit counts as $0).

Results.

  • Interest in the first month = the starting balance × monthly rate (the first deposit comes at the end of month 1, so it earns nothing that month).
  • Total interest = the interest of every month added up.
  • Average interest a month = total interest ÷ number of months.
  • Interest in the last month = the interest of the final month.
  • Ending balance = the balance after the last month = money put in + total interest.
  • Money put in = starting balance + deposit × number of months.
  • APY = (1 + r ÷ m)^m − 1.

Limits. Balance from $0 to $1 billion; rate from 0% to 100%; deposit from $0 to $100 million a month; 1 to 600 months.

Display. Money to the cent, rounded half up from the value worked out (nothing is rounded between months); the monthly rate to 6 decimals and the APY to 4.

Assumptions

  • The rate stays the same for every month.
  • Deposits are added at the end of each month.
  • Tax on interest and account fees are not included.

Worked examples by hand

$10,000 at 5%, monthly compounding, 12 months. Monthly rate = 0.05 ÷ 12 = 0.4166667%. First month = 10,000 × 0.004166667 = $41.67. After 12 months the balance is 10,000 × 1.0041667^12 = 10,000 × 1.0511619 = $10,511.62, so the total interest is $511.62 and the APY 5.1162%. The last month earns $43.62.

$25,000 at 4%, daily compounding, 12 months. Monthly rate = (1 + 0.04 ÷ 365)^(365 ÷ 12) − 1 = 0.33387118%. First month = 25,000 × 0.0033387118 = $83.47. APY = (1 + 0.04 ÷ 365)^365 − 1 = 4.0808%, so the year earns 25,000 × 0.0408085 = $1,020.21.

$100 deposited at the end of each month at 6%, 12 months. Monthly rate = 0.5%. Ending balance = 100 × (1.005^12 − 1) ÷ 0.005 = $1,233.56. Money put in = $1,200, so the interest is $33.56, an average of $2.80 a month. The first month earns $0, because the first deposit arrives at its end.

$10,000 at 6%, yearly compounding, 24 months. Monthly rate = 1.06^(1/12) − 1 = 0.4867551%. After 24 months: 10,000 × 1.06² = $11,236.00, the same as yearly compounding gives, with $1,236 of interest.

Other questions people ask

How do I calculate monthly interest?

With monthly compounding, divide the yearly rate by 12 and multiply by the balance. $10,000 at 5% a year earns 10,000 × 0.05 ÷ 12 = $41.67 in the first month. The next month earns a little more, because last month’s interest earns interest too: $511.62 over the first year.

How is monthly interest worked out with daily compounding?

Interest is added every day at the yearly rate ÷ 365, so over a month the balance grows by (1 + rate ÷ 365)^(365 ÷ 12) − 1. At 4% that is 0.33387% a month: $83.47 on $25,000 in the first month.

What is the difference between the interest rate and the APY?

The interest rate is the yearly rate before compounding. The APY (annual percentage yield) is what the balance actually grows in a year once interest earns interest: (1 + rate ÷ m)^m − 1 for m compoundings a year. 5% compounded monthly is an APY of 5.1162%. If your bank quotes an APY, use the money market or savings calculator, which take an APY.

Why does each month earn a different amount of interest?

Because the balance grows. Each month’s interest is added to the balance, and deposits add to it too, so the next month earns interest on a larger amount. At 5% on $10,000 with no deposits, month 1 earns $41.67 and month 12 earns $43.62.

How much interest does $100,000 earn a month?

At 5% compounded monthly, $100,000 earns $416.67 in the first month. At 4% it earns $333.33. Type your own balance and rate for your account.

Does this work for a loan?

The first month’s interest is the same idea: a $10,000 loan at 5% a year charges about $41.67 in its first month. But loan payments lower the balance, so later months charge less. Use the amortization or loan calculator to see a loan month by month.