Understand the assumptions behind every projection.

How to use

Test assumptions in a useful order.

Start with the money you can invest, a time horizon, and a cautious return assumption. Then change one input at a time to see what matters most.

1. Set an initial amount and a regular contribution.
2. Choose return, inflation, and annual-cost assumptions.
3. Compare cautious and central cases before treating any result as a plan.

Inflation

Nominal returns are not purchasing power.

A nominal return describes growth in future currency. Inflation changes what that currency can buy, so a long-term plan should compare both views.

Inputs

Start with the choices you can inspect.

A useful scenario names its starting balance, regular contribution, time horizon, expected annual return, costs, and inflation assumption.

• Starting balance: money invested at the beginning.
• Contribution: the amount added regularly and when it is added.
• Horizon: the years before you expect to need the money.
• Return, fees, and inflation: assumptions, not facts.

Contributions

Consistency can matter more than a perfect entry date.

Regular contributions add new capital throughout the plan. Increasing, pausing, or stopping them can change the outcome more than a small change in the assumed return.

• Initial investment: starts compounding immediately and stays exposed for the full horizon.
• Monthly contribution: a budgeting input. This calculator groups three months into each quarterly DCA purchase; it does not model monthly purchases. Read the contribution schedules.
• Contribution pause: reduces contributed principal and the time that missed deposits could have compounded.

Fees

Costs compound too.

Fund fees and other investing costs reduce the return left to compound. A 0.20% annual cost turns a 6.00% gross-return assumption into roughly 5.80% before taxes and other costs.

Funding path

DCA and lump sum answer different questions.

A lump sum is exposed to market movements immediately. Phased investing spreads purchases over time. Neither removes market risk, and the calculator cannot determine the right choice for your circumstances.

Reading results

Separate your money from the modelled growth.

The final portfolio estimate combines your contributions with modelled returns after the selected costs. Read the supporting values before focusing on the headline number.

• Total contributed: the principal added by you over the selected period.
• Projected growth: the modelled difference between the portfolio estimate and contributed principal.
• Nominal value: future euros before adjusting for changes in purchasing power.
• Real value: an inflation-adjusted comparison expressed in today-like purchasing power.

Small differences are not precise predictions. Use the comparison to understand direction and sensitivity, not to rank nearly identical scenarios.

Uncertainty

Use ranges, not promises.

Run cautious, central, and optimistic assumptions. Also test a lower contribution, higher inflation, and a temporary pause. Sensitivity matters more than a single final number.

Before using a result

Turn one projection into a planning range.

1. Use a contribution that remains affordable after essential spending and emergency savings.
2. Check that the horizon matches when you may realistically need the money.
3. Compare at least a cautious case with lower growth and higher inflation.
4. Review fees, ETF type, taxes, and other costs that the simplified scenario may not include.
5. Revisit the assumptions when your income, goals, time horizon, or costs change.

Glossary

Words used in this guide.

Deep dives

Continue with one focused question.

Each article connects the calculator's model to a specific planning decision, with worked examples, limitations, and primary sources.