Index fund calculator

How much would you have if you had invested every month in an index fund? With the actual prices of recent years, not a made-up %. And how much of it the fee takes.

The fee starts at the fund's own; an actively managed bank fund usually charges between 1 and 2%. The projection return starts at what the fund has done so far, before fees.

For real, from 11/2016 to 11/2026

51.161 € MSCI World

You put in
25.000 €
Gain
26.161 €
Worst drawdown
-16,9% from €10.564 to €8.777 (01/2020 → 03/2020)

Paying 0,20% instead of 0,1% would have cost you €315.

In 10 years, at 12,4% a year before fees (12,2% after)

47.951 €

You put in
25.000 €
Gain
22.951 €

Paying 0,20% instead of 0,1% would cost you €297.

Past returns do not guarantee future returns. This is not investment advice or a recommendation: it is arithmetic on past prices, and the list of funds is illustrative.

Source: monthly closes adjusted for dividends from Yahoo Finance, up to 02/11/2026; fee (TER) from each ETF's official factsheet.

What an index fund is

A fund that doesn't try to pick stocks: it buys all the stocks of an index (the MSCI World, the S&P 500, the IBEX 35…) in the same proportion and follows its result, good or bad. Since it pays no team to pick, it charges much less: between 0.05 and 0.3% a year, against 1.5-2% for a typical actively managed fund.

Why the fee matters so much

It is charged every year on everything you have, not on what you earn. €200 a month for 30 years at 7% before costs: with a 0.1% fee you end up with about €229,000; with 1.5%, about €175,000. The fee kept more than €54,000. With your own numbers, the calculator tells you in euros.

Frequently asked questions

Which funds are in the calculator?

One index ETF traded in euros for each major market: the developed world (MSCI World), the US (S&P 500), Europe (STOXX Europe 600), emerging markets, Japan and Spain (IBEX 35). The list is illustrative, to see how each market has behaved: it is not a selection or a ranking, and it is not a recommendation.

How is the historical simulation calculated?

The initial amount goes in the first month and the monthly contribution at the end of each month, at the real price of that moment. If you enter a fee different from the fund's, the fund's fee is added back and yours is taken off, month by month. The worst drop is the largest fall of your balance from a previous high. Taxes and purchase fees are not included.

Does the projection tell me what I will earn?

No. It applies the same return every year, and no market gives a fixed one: the real path has years of −20% or −40% along the way. By default it uses the annual return the fund has made so far, which can be very different from what it will make. Past returns do not guarantee future returns.

Where does the data come from?

From each ETF's daily quote on Yahoo Finance: the close adjusted for dividends and splits, taking the last one of each month. The fee (TER) is the one on each ETF's official factsheet. They are euro ETFs so that the result includes the currency effect as a euro-area investor lives it.

Index fund or ETF: what's the difference?

They follow the same index and have similar costs. The ETF trades on the stock exchange and is bought through a broker; the index fund is bought from the manager or a platform and, in Spain, can be switched to another fund without paying tax at that moment. ETFs are used here because their daily price is public.

And then, track it for real

Arvenyx has a page for every fund and ETF (fee, return each year, drawdowns) and, if you log your contributions, the real return of your portfolio. Free.

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