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Investment Growth Calculator

Project a portfolio with contributions, fees taken out each year, and the result in today’s dollars.

Enter a starting amount or monthly contribution to project the balance.

Before fees. Broad stock indexes have averaged roughly 7% real over long periods, with wide variation.

The things that quietly matter

Charged against the balance every year. Index funds are often under 0.10%; actively managed funds are frequently above 0.75%.

Used to show the result in today's purchasing power.

If you contribute a fixed share of a rising salary.

Projection. Depends on the future. Useful for planning, never a promise.

How this calculator works

A monthly simulation with two things most growth calculators leave out, because both quietly consume a large share of a long-run result.

**Fees.** The expense ratio is charged against the balance every month, exactly as a fund does. That means the fee compounds against you the same way returns compound for you — which is why a 1% expense ratio over thirty years costs far more than 1% of the final balance, often 20% or more.

**Inflation.** The result is shown in nominal dollars and in today’s dollars. A $1.4 million balance in 2056 is not $1.4 million of purchasing power, and showing only the nominal figure makes every plan look better than it is.

Contributions can grow each year, which is what happens when you save a fixed share of a rising salary.

The formula

Exactly what happens to your numbers, step by step.

  1. Each month

    growth  = balance × (annual return ÷ 12)
fee     = (balance + growth) × (expense ratio ÷ 12)
balance = balance + growth − fee + contribution

  2. In today’s dollars

    real balance = nominal balance ÷ (1 + inflation)^years

A worked example

$10,000 to start, $500 a month, 7% return, 20 years, with a 1% expense ratio and 2.5% inflation.

What you enter

Starting
$10,000
Monthly
$500
Return
7%
Expense ratio
1.00%
Inflation
2.5%

The working

Total invested
$130,000
Balance with no fee
≈ $299,000
Balance with 1% fee
≈ $261,000
Cost of the fee
≈ $38,000
In today's dollars
≈ $159,000

About $261,000 nominal — roughly $159,000 in today’s money

The 1% fee costs about $38,000, which is nearly 30% of everything you contributed. Switching to a 0.05% index fund keeps almost all of that. Meanwhile inflation halves the apparent size of the result.

Assumptions

Every result here rests on these. Change your inputs and the result changes with them.

  • One constant rate of return every year. Real markets do not behave this way.
  • Contributions are made at the end of each month.
  • The expense ratio is charged monthly against the balance.
  • No taxes on growth. In a taxable account, dividends and realised gains are taxed along the way.

What this cannot tell you

  • **This is a projection, not a forecast.** It cannot tell you what markets will do.
  • Sequence of returns is not modelled. Whether the bad years come early or late materially changes real outcomes, especially near retirement.
  • It does not model contribution limits, employer matches or asset allocation.

Questions people ask

What return should I assume?

There is no right answer. Broad U.S. stock indexes have averaged roughly 10% nominal and 7% after inflation over very long periods, with enormous variation between decades. Many planners use 6% to 7% as a conservative long-run assumption.

Does a 1% fee really matter?

Enormously. It is charged on the whole balance every year, so it grows as your portfolio does. Over decades a 1% ratio typically consumes 20% to 25% of the final balance compared with a low-cost index fund.

Why show the result in today’s dollars?

Because that is the only figure that tells you what the money will buy. A million dollars in thirty years at 2.5% inflation has the purchasing power of about $477,000 today.

Is this investment advice?

No. It is arithmetic on assumptions you supply. It cannot account for your circumstances, tax position or risk tolerance, and it is not a recommendation to invest in anything.

Related calculators

Sources and review

This calculator uses standard arithmetic with no external rules or published rates, so there is nothing to cite beyond the formulas shown above.

Methodology version 1.0.0 · Last reviewed