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Compound Interest Calculator

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

Processed in your browser — files never leave your device

Balance after 20 years

$300,850.72

You put in
$130,000.00
Interest earned
$170,850.72

Deposits 43%Interest 57%

Year by year

YearYou put inInterest earnedBalance
1$16,000.00$919.19$16,919.19
2$22,000.00$2,338.58$24,338.58
3$28,000.00$4,294.31$32,294.31
4$34,000.00$6,825.16$40,825.16
5$40,000.00$9,972.70$49,972.70
6$46,000.00$13,781.53$59,781.53
7$52,000.00$18,299.43$70,299.43
8$58,000.00$23,577.68$81,577.68
9$64,000.00$29,671.22$93,671.22
10$70,000.00$36,639.02$106,639.02
11$76,000.00$44,544.25$120,544.25
12$82,000.00$53,454.70$135,454.70
13$88,000.00$63,443.02$151,443.02
14$94,000.00$74,587.14$168,587.14
15$100,000.00$86,970.62$186,970.62
16$106,000.00$100,683.03$206,683.03
17$112,000.00$115,820.45$227,820.45
18$118,000.00$132,485.91$250,485.91
19$124,000.00$150,789.85$274,789.85
20$130,000.00$170,850.72$300,850.72

Estimate at a fixed rate, before tax, fees and inflation. Not financial advice.

How to use the calculator

  1. Enter what you start with and how much you will add each month.
  2. Enter the yearly interest rate and the number of years.
  3. Pick how often interest is compounded. The table shows your balance at the end of every year.

The formula

Money P at a yearly rate r compounded n times a year grows to P × (1 + r/n)^(n × t) after t years. Monthly deposits are added on top, each growing from the month it goes in.

Example

Start with $10,000, add $500 a month at 7% for 20 years: you put in $130,000 and end with about $301,000. More than half of the final balance is interest, and most of it arrives in the last ten years. Time does the heavy lifting.

Ways to grow faster

  • Start early: ten extra years matter more than a slightly higher rate.
  • Increase the monthly deposit when your income rises.
  • Keep fees low; a 1% yearly fee takes a large share over decades.

Questions and answers

When are the monthly deposits added?
At the end of each month, after that month’s interest. This is the usual assumption for savings plans.
Does compounding frequency matter much?
A little. At 7% a year, $10,000 grows to about $19,672 in 10 years compounded yearly and about $20,097 compounded monthly.
Are taxes, fees and inflation included?
No. The result is before tax and fees, in today’s money. Real returns are usually lower.
Is this financial advice?
No. It is an estimate based on a fixed rate. Real investments go up and down.

Updated November 14, 2026