Investment Calculator

Written byOleh Soloninupdated 5 October 2026

Currency

What to work out

Starting amount

Monthly contribution

Return, % a year (effective)

The annual return after compounding. A 16% deposit compounded monthly is 17.23%: (1 + 16% ÷ 12)¹² − 1.

Term, years

Advanced options

Inflation, % a year

Raise the contribution each year, %

For example with inflation or pay rises: at 5% a 500 contribution becomes 525 in the second year.

Tax on gains

Tax is charged on the gain over the whole term, as if everything were sold in the last year. Allowances are not included.

Yearly withdrawal, % of capital

For the income line: the share of the capital taken out each year.

Result

Final balance

$292,465.03

Paid in

$130,000.00

Growth

$162,465.03

Times larger

2.25

In today's money

$161,930.80

Income from the capital a month

$974.88

That income in today's money

$539.77

Working

Monthly rate: (1 + 7%)^(1/12) − 1 = 0.5654% 10,000 × (1 + 0.5654%)^240 + 500.00 × ((1 + 0.5654%)^240 − 1) ÷ 0.5654% = 292,465.03

Year by year

Year         Paid in          Growth         Balance     Today's money
   1          16,000             890          16,890            16,398
   2          22,000           2,263          24,263            22,870
   3          28,000           4,151          32,151            29,423
   4          34,000           6,592          40,592            36,065
   5          40,000           9,623          49,623            42,806
   6          46,000          13,287          59,287            49,652
   7          52,000          17,627          69,627            56,614
   8          58,000          22,692          80,692            63,699
   9          64,000          28,530          92,530            70,917
  10          70,000          35,197         105,197            78,277
  11          76,000          42,751         118,751            85,788
  12          82,000          51,254         133,254            93,462
  13          88,000          60,772         148,772           101,307
  14          94,000          71,376         165,376           109,333
  15         100,000          83,143         183,143           117,552
  16         106,000          96,153         202,153           125,975
  17         112,000         110,494         222,494           134,612
  18         118,000         126,258         244,258           143,476
  19         124,000         143,547         267,547           152,578
  20         130,000         162,465         292,465           161,931

Balance at other returns

    Return         Balance          Growth     Today's money
        4%         203,832          73,832           112,857
        6%         258,791         128,791           143,286
>       7%         292,465         162,465           161,931
        8%         331,109         201,109           183,327
       10%         426,405         296,405           236,090
       12%         552,068         422,068           305,667
       15%         819,519         689,519           453,748

This result is informational only and is not professional advice.

What you will have, what to put in, and what is left after tax and inflation

Investment calculator with monthly contributions: what you will have, how much to invest each month for a goal, how many years a goal takes, tax on gains, the result and income in today's money, and tables by year and by return.

This calculator builds a plan of regular investing: it works out the balance with compound growth and a contribution every month, separates what you paid in from what the money earned, and shows what the total is worth in today's money.

You can also start from a goal: find the monthly amount that reaches it by a date, or how long your current contribution takes to get there. Tax on gains, contributions that rise each year and the income the capital could pay are in the extra settings.

How to use

Choose the task: how much you will have, the monthly investment for a goal, or the years a goal takes.
Enter the starting amount, the contribution or goal, the yearly return and the term.
In the extra settings add inflation, a yearly rise in the contribution, a tax rate on gains and the share of the capital you plan to withdraw each year.
Read the balance, the growth, any tax, the result in today's money and the tables by year and by return.

How the balance grows with monthly contributions

Balance = S × (1 + i)ⁿ + P × ((1 + i)ⁿ − 1) ÷ i, where S is the starting amount, P the contribution at the end of each month, n the number of months and i the monthly return. The yearly return r becomes a monthly one that compounds to exactly r over 12 months: i = (1 + r)^(1/12) − 1. At 7% a year that is 0.5654% a month.

10,000 to start and 500 a month at 7% for 20 years grows to 292,465.03. You paid in 130,000 and the money earned 162,465.03, so the balance is 2.25 times your contributions. The Working line shows this formula with your numbers, and the Year by year table shows how the balance builds.

10,000 to start, 500 a month, 7% a year, before tax. Worked out with this calculator.
Year	Paid in	Growth	Balance
1	16,000	890	16,890
5	40,000	9,623	49,623
10	70,000	35,197	105,197
15	100,000	83,143	183,143
20	130,000	162,465	292,465

How much to invest for a goal, and how long it takes

To reach 500,000 in 20 years from a 10,000 start at 7%, you need to invest 908.91 a month. At 500 a month the same goal takes 26 years 6 months.

A goal can be set in today's money, and the calculator then inflates it to the final year: 500,000 at today's prices is 903,055.62 after 20 years of 3% inflation, which needs 1,703.05 a month.

Inflation: what the total is worth today

To express a future sum in today's money, divide it by (1 + inflation)ⁿ. At 3% a year prices rise 1.81 times over 20 years, so 292,465.03 buys what 161,930.80 buys today. The Today's money column in the table by year applies the same adjustment.

If your pay rises, the contribution can rise too. Increasing it by 3% a year (500 a month in year one, 515 in year two) builds 358,042.47 over 20 years instead of 292,465.03, with 171,222.25 paid in.

Tax on investment gains

Tax rules depend on where you live and on the account, so the calculator takes your own rate and charges it once on the whole gain, as if everything were sold in the final year. At 15%, the gain of 162,465.03 costs 24,369.75 in tax and leaves 268,095.28. Allowances and tax-free accounts are not modelled. The Russian income tax option applies the Russian rates: 13%, and 15% on the part above 2.4 million roubles a year of investment income such as securities gains and deposit interest. Dividends are taxed at the same rates but against a threshold of their own: they stay out of that total for the other income (Article 225(1.1) of the Tax Code), and the other income stays out of theirs (Article 214(3)).

10,000 to start, 500 a month, 7% a year, 3% inflation; tax charged on the whole gain in the last year. Worked out with this calculator.
Term	Growth	Tax at 15%	After tax	In today's money
10 years	35,197.38	5,279.61	99,917.77	74,348.21
20 years	162,465.03	24,369.75	268,095.28	148,437.86
30 years	470,848.85	70,627.33	590,221.52	243,163.45

What return to assume

The calculator does not forecast returns and treats the one you enter as constant, while real returns vary from year to year. It is safer to compare several: the Balance at other returns table reruns your plan at 4, 6, 8, 10, 12 and 15%. The return here is an effective annual one, compounding included: for a savings account use its AER or APY rather than the nominal rate, and for bonds their effective yield to maturity.

10,000 to start, 500 a month, 20 years, 3% inflation, before tax. Worked out with this calculator.
Return	Balance	Growth	In today's money
4%	203,832	73,832	112,857
6%	258,791	128,791	143,286
7%	292,465	162,465	161,931
8%	331,109	201,109	183,327
10%	426,405	296,405	236,090
12%	552,068	422,068	305,667

Income from the capital

The income line is the balance after tax × the share you withdraw each year ÷ 12. Withdrawing 4% a year of 268,095.28 gives 893.65 a month, but in today's money that is 494.79, and that is the figure to plan spending with. The withdrawal share can be changed in the extra settings.

Whether the capital lasts at that rate is not something this calculator judges: it depends on returns and inflation in the years you draw on it. To plan savings for a target income, use the retirement calculator.

What this calculator shows

The final balance, what you paid in, the growth and the multiple
The monthly amount for a goal, or the time a goal takes
Tax on the gain at your rate and the balance after tax
The balance and the income from it in today's money
Tables by year and at other returns

What to keep in mind

The return is constant, contributions go in at the end of each month, and the monthly rate is (1 + r)^(1/12) − 1.
Tax is charged once on the whole gain; allowances, tax-free accounts and fees are not included.
Today's money and the income line use the balance after tax; the tables are before tax.
A yearly rise in the contribution applies from month 13, month 25 and so on.

Where the numbers come from

Checked against the compound growth formula with monthly contributions · verified September 2026.

FAQs

How do I calculate investment growth with monthly contributions?

Balance = S × (1 + i)ⁿ + P × ((1 + i)ⁿ − 1) ÷ i, with i the monthly return. 10,000 plus 500 a month at 7% a year for 20 years comes to 292,465.03, of which 162,465.03 is growth.

How much do I need to invest each month to reach 500,000?

From a 10,000 start at 7% a year, 908.91 a month for 20 years. If the 500,000 is in today's money and inflation is 3%, it is 1,703.05 a month. Choose the goal option and enter your own term and return.

How many years will it take to reach my goal?

Choose the years option. With 10,000 to start, 500 a month and 7% a year, 500,000 takes 26 years 6 months.

How does inflation change the result?

Divide the balance by (1 + inflation)ⁿ. At 3% over 20 years the divisor is 1.81, so 292,465.03 is worth 161,930.80 in today's money. You can also set the goal itself in today's money.

Is it better to invest a lump sum or monthly?

At a constant return, a lump sum ends higher because it is invested for longer: 120,000 at 7% for 20 years grows to 464,362.14, while the same money at 500 a month grows to 253,768.19. Real returns vary, so the outcome also depends on which years the money was invested in.

Why raise the contribution every year?

So that it keeps pace with rising pay and prices. A 3% yearly rise turns 500 a month at 7% over 20 years into 358,042.47 instead of 292,465.03.

How is tax on the gain handled?

Enter your rate and the calculator charges it once on the whole gain, as if you sold in the last year. At 15%, 162,465.03 of growth costs 24,369.75. Allowances and tax-free accounts are not included, so check your own country's rules.

What return should I use?

The one your investment actually offers, as an effective annual figure: a savings account's AER or APY, or a bond's effective yield to maturity. Returns on shares are not guaranteed, so compare scenarios in the table of other returns: at 6% instead of 7% the example ends at 258,791 instead of 292,465.

Worked example

500 a month for 20 years

Input: 10,000 to start, 500 a month, 7% a year, 20 years, 3% inflation

Output: 292,465.03, of which 130,000 paid in and 162,465.03 growth

Note: In today's money that is 161,930.80. With 15% tax on the gain, 268,095.28 is left.

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