Data / Scenario calculator

Investment calculator with inflation

What could a starting amount and regular savings become? Set your own assumptions to compare the future balance with what it could buy at today’s prices, and see the effect of an annual balance fee.

Method updated 2 November 2026. Assumptions only; no market observations.

Compare two annual fees

All amounts are in euros (€); no currency conversion is made. Payments go in at the end of each month and stay fixed in nominal euros.

The starting figures are illustrations. Every future rate is your assumption, not a forecast or a recommended return.

Your scenario

Total paid in, nominal
Final nominal balance, after fee
Final balance in today’s money, after fee
Fee drag, nominal

The nominal path: balances and money paid in

All three lines use nominal euros. For today’s purchasing power, read the separate columns below. Figures are rounded to cents; the calculation is not.

Show yearly figures and the final month

Start, each full year and the endpoint. “Today’s money” means prices at the start of this scenario.
Elapsed	Paid in nominal	Balance after fee, nominal	Balance no fee, nominal	Balance after fee, today’s money	Paid in today’s money

Compare two annual fees

Run one savings scenario twice and change only the annual fee on the balance. The return, payments and dates stay the same.

Every rate is your assumption. The opening fee levels are example inputs, not typical charges for any fund or product, and this doesn’t predict how any fund would perform.

The comparison

Total paid in, nominal
Final balance, fee A
Final balance, fee B
Difference, nominal

Paid in, today’s money
Fee A, today’s money
Fee B, today’s money
Difference, today’s money

A fee takes a share of the whole balance, including past growth, and what it takes stops growing. So the gap widens over time and includes that lost growth as well as the charges themselves.

Both balances and the money paid in, nominal euros

Source: your assumptions, not market data. Method dated 3 November 2026. Figures are rounded to cents; the calculation is not.

Show yearly figures and the final month

How the fees are charged

Monthly balance = previous balance × [(1 + return) × (1 − fee)]^1/12 + monthly payment.

This spreads each year’s fee across its months. It’s an approximation: real funds charge in their own ways, and a published ongoing charge or TER isn’t automatically the whole cost of investing.
The starting amount is invested at once. Each monthly payment arrives after that month’s growth and fee, so it bears a fee only from the month it goes in, never for earlier years.
Both scenarios use the same gross return. In practice, funds with different fees can also earn different returns before fees.
Today’s money means prices at the start of the scenario. Balances are divided by the inflation factor at the end, and each payment by the factor at the month it goes in, so both are on the same price basis.
Tax, dealing costs, fixed platform fees and market ups and downs aren’t included. It’s an illustration, not advice.

Assumptions and method

The starting amount is invested immediately. Each monthly payment arrives after that month’s growth and fee, so the final payment has no time to earn a return or incur a fee. A zero-month horizon includes only the starting amount. The monthly payment does not rise with inflation.

Return and inflation are constant annual effective assumptions. They may be negative, but must be above −100%. The fee is a fraction of the balance, from 0% to below 100%. This smooth path leaves out market fluctuations, taxes, transaction charges and fixed account fees. It is a scenario, not a prediction or a product quotation.

Growth and the fee

We use an annual-factor approximation: the net annual growth factor is (1 + gross return) × (1 − annual fee). The monthly factor is its twelfth root. This spreads the fee’s effect across the months rather than deducting a bill once a year. Actual charging schedules can differ.

Monthly balance = previous balance × [(1 + r) × (1 − f)]^1/12 + monthly payment.

Here, r and f are annual rates as decimals: 5% is 0.05. With a 5% gross return and 1% fee, the annual factor is 1.05 × 0.99 = 1.0395: a 3.95% net return. The no-fee comparison uses the same starting amount, payment dates, horizon and gross return, with f = 0. Fee drag is the difference between the two ending balances, including its compounding effect.

Today’s purchasing power

For n months and assumed annual inflation i, the price factor is (1 + i)^n/12. The real ending balance is the nominal ending balance divided by that factor. “Today” is the start of your scenario, not a future endpoint.

We also divide each payment by the inflation factor at the month it enters the account. Total contributions in today’s money are the starting amount plus the sum of those discounted payments. The real gain or loss compares this total with the real ending balance. This keeps both sides at the same prices.

For example, with no starting amount, zero return and no fee, one €100 payment at the end of one year with 10% annual inflation has a value of €90.91 in start-date money. Its ending balance is also €90.91 on that basis, so the real gain is zero. The calculator applies this principle to each monthly payment separately.

Limits: amounts up to €1 billion each; a horizon up to 100 years in whole months; annual return and inflation up to 1,000%. Combinations producing values above €1,000 trillion are rejected. Values are calculated without rounding, then shown to the nearest cent.

Sources and a different view of inflation

The ECB’s explanation of inflation describes how price rises reduce purchasing power and why households experience them differently. The US SEC’s bulletin on investment fees (23 July 2025) explains how fees reduce the balance left to compound. These explain the concepts; the scenario uses your inputs and the method above, with no official rate carried forward.

For observed history, use the euro inflation calculator. Its inflation-adjusted view restates historical balances and payments in end-month euros using observed HICP. This tool instead discounts a hypothetical future back to prices at the start.

Source explanations checked 2 November 2026.