Tool

How money adds up, and how wide the range is

Set your own assumptions and see two things at once: how compounding grows over the years and how uncertain the actual outcome is. Switch on the randomness view and instead of one smooth line you get a range of possible paths, including the bad ones.

Starting amount The amount you start with.

Recurring contribution How much you add regularly.

Contribution frequency Monthly contributions are summed into a yearly amount for the calculation.

Time horizon (years) How many years you leave the money invested.

Return scenario Your assumption about the long-run yearly return. You can adjust it below.

When on, shows a range of paths instead of one line.

Uncertainty model "By periods" adds calm, normal and stress periods.

Advanced: assumptions

Expected real return per year In today's money, so inflation is already taken out.

Volatility (annual std. dev.) Higher volatility means a wider range of outcomes.

€87,964

Middle outcome after 20 years

€35,416 to €166,108

Range (p5 to p95)

21.0%

Chance of ending below what you put in

With these assumptions the middle outcome is about €87,964. Half the simulations end between €62,592 and €117,855, but the range runs from €35,416 to €166,108. About 21% of simulations end below €58,000, that is, below everything you put in. Uncertainty is part of the picture, not a flaw.

Range of possible outcomes over the years
Year	p5	median	p95
0	€10,000	€10,000	€10,000
3	€12,397	€18,708	€23,139
6	€16,318	€28,343	€38,512
9	€20,237	€39,099	€57,165
12	€23,773	€51,022	€80,204
15	€28,042	€64,003	€107,786
18	€32,105	€77,904	€140,770

What this assumes

Average annual return (real): approx. 3.9%
Annual variability: approx. 13%
Method: 5,000 simulations (Monte Carlo)

In the model the market is not smooth: it moves between calm (+8%), normal (+4%) and stress (-12%) years, and the figures above are the long-run average across all simulations. Because returns vary, money compounds a little more slowly than this average. All figures are real (in today's money). These are illustrative assumptions you can change, not a forecast and not JonatanMars Invest performance.

This calculation is only an illustration based on the assumptions you entered and publicly available data. It is not investment advice, a personal recommendation, or a forecast or promise of returns. It does not represent JonatanMars Invest performance. Outcomes are uncertain and may differ materially from the actual result.

The return and volatility assumptions are yours and you can change them. They draw on long-run third-party estimates and are not a forecast.
The paths shown are simulations, not actual returns and not JonatanMars Invest performance. Markets behave differently from any single simulation.
The calculation is in real terms (today's money). Investing carries risk and you may lose part or all of what you put in.

Capital at risk. Investing involves risk: the value of investments can go down as well as up, and you may get back less than you invested. Past performance and any simulated/back-tested performance are not reliable indicators of future results. Tax treatment depends on individual circumstances and current law, both of which can change. This website is a marketing communication. It is not investment advice, a personal recommendation, or an offer to enter into any contract. Detailed pre-contractual information is provided before any agreement is concluded.

Questions about how this would look for you?

Uncertainty does not disappear, but it can be managed. Book a no-obligation conversation and let us look together at what makes sense for your situation.

Book a conversation How we manage money