Compound interest calculator

Enter what you have now, what you can add each month and a growth rate. See what it could become, how much of that is growth, and what waiting a few years would cost.

Your numbers

CurrencyStarting amount$Added each month$Expected yearly return%Before inflation. Lower it by any yearly fees.How longyearsRaise the monthly amount each year by%Optional. 0 keeps it the same every year.Money goes in at theInflation per year%Used to show the result in today's money.Compare starting later byyears

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Balance after 20 years

$108,224

About 55% of it is growth

Money you put in

$49,000

Growth earned

$59,224

In today's money

$59,921

At 3% inflation a year

Cost of starting 5 years later

$41,983

You would end with $66,241

Balance and money put in, year by yearBalancePut in

See the year-by-year table

Year	Put in so far	Growth so far	Balance
1	$3,400	$151	$3,551
2	$5,800	$486	$6,286
3	$8,200	$1,019	$9,219
4	$10,600	$1,764	$12,364
5	$13,000	$2,736	$15,736
6	$15,400	$3,952	$19,352
7	$17,800	$5,430	$23,230
8	$20,200	$7,188	$27,388
9	$22,600	$9,246	$31,846
10	$25,000	$11,627	$36,627
11	$27,400	$14,353	$41,753
12	$29,800	$17,450	$47,250
13	$32,200	$20,944	$53,144
14	$34,600	$24,864	$59,464
15	$37,000	$29,241	$66,241
16	$39,400	$34,109	$73,509
17	$41,800	$39,501	$81,301
18	$44,200	$45,457	$89,657
19	$46,600	$52,017	$98,617
20	$49,000	$59,224	$108,224

How this calculator works

Each month, your balance grows by one twelfth of the yearly rate, then your monthly amount is added (or added first, if you choose the start of the month). Growth is earned on earlier growth too. That snowball is compound interest.

The yearly increase raises your monthly amount once a year, for example by 5% when your pay goes up. In India this is often called a step-up SIP. In the US people call regular investing dollar-cost averaging, and in the UK a regular savings plan. The maths is the same.

An example

Start with 1,000 and add 200 a month for 20 years at 7% a year. You put in 49,000 in total. At a steady 7%, the balance comes to roughly 108,000, so more than half of it is growth, and most of that growth arrives in the final ten years.

What changes the result most

Time. Growth needs years to compound. The cost-of-waiting figure shows how much a late start removes, even when you save the same amount each month.
The rate. One or two percentage points look small but add up over decades. Fees count against the rate, so a 1% yearly fee on a 7% return leaves about 6%.
Inflation. A future amount buys less than it does today. Switch on today's money to see the balance in present-day prices.

Questions people ask

What growth rate should I use?

Use a rate you can justify, not the best year you remember. Savings accounts and bonds usually pay less than shares, and shares move up and down from year to year. Try a low, middle and high rate to see a range rather than a single answer.

Does this include taxes and fees?

No. Lower the rate by your yearly fees to allow for them. Taxes depend on your country and account type, so check your own rules.

Is monthly compounding right for my account?

Many accounts compound daily or monthly. The difference over years is small next to the effect of the rate itself, the amount you add and how long you leave it.

Why does starting later cost so much?

The money you would have added early has the most years to grow. Starting later removes those years, and the growth those years would have earned on top.

For education only, not financial advice. Results are estimates from the numbers you enter. Returns are illustrative, not a forecast or a promise, and real results depend on fees, taxes, timing and your lender's or provider's exact terms. See our editorial policy.

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