How fees compound
A fee of 1% a year sounds small. Over decades it takes a far larger share of the final balance than the percentage suggests. Here is the arithmetic.
Why a small percentage is not small
A fee is usually quoted as a percentage of what you hold, charged every year. One percent sounds like a rounding error. But it is taken from the whole balance, not just from the growth, and next year it is taken again from a balance that is already smaller than it would have been.
That is compounding working against you. Every amount a fee removes also stops earning a return for every year that follows, so the gap between the balance you have and the one you would have had widens faster each year.
A useful way to see the size of it: if an investment returns 7% a year before costs, a 1% fee does not take one percent of your result. It takes about one seventh of each year's growth.
A worked example
Take $10,000 and leave it to grow at 7% a year, compounded annually, with nothing added. Then take the same amount at 6% — the same investment with a 1% yearly fee taken off the return — and compare the two as the years pass.
| After | At 7% | At 6% | Cost of the fee |
|---|---|---|---|
| 10 years | $19,672 | $17,908 | $1,763 |
| 20 years | $38,697 | $32,071 | $6,625 |
| 30 years | $76,123 | $57,435 | $18,688 |
After ten years the fee has cost 9% of what the balance could have been. After twenty years it has cost 17%, and after thirty, 24.5% — nearly a quarter — even though the fee itself never changed from one percent.
Other fee levels follow the same pattern. Over the same thirty years a 0.5% fee costs about 13% of the final balance, and a 2% fee costs about 43%.
With regular contributions
Most people do not invest a single amount and walk away. With the calculator's own defaults — $10,000 to start and $1,000 a month — thirty years at 7% reaches $1,252,632. At 6%, the same deposits reach $1,036,966.
The difference is $215,666, about 17% of the final balance. Regular deposits soften the effect a little, because the most recent ones have not been charged for long. Measured against the interest alone, though, the fee still takes about 24% of everything the money earned.
Where fees come from
The cost of holding an investment is rarely a single number. The usual parts are:
- Fund charges. An ongoing charge or expense ratio taken inside the fund, so it never appears as a separate line on a statement.
- Platform or account fees. A yearly percentage, or a fixed amount, for holding the account.
- Advice or management fees. A percentage paid to someone who chooses or rebalances the investments.
- Trading costs. Commissions, the spread between buying and selling prices, and currency conversion.
The percentages add up. A fund charging 0.6% held on a platform charging 0.4% costs 1% a year in total, which is the example above.
Checking it with the calculator
The compound interest calculator shows growth before costs. To see what a fee does, run the same figures twice: once with the return you want to test, and once with the total yearly fee subtracted from it. Subtracting is a close approximation rather than an exact one, and the difference between the two final values is roughly what the fee costs over that period.
Inflation eats into a return in a very similar way — see inflation and real returns. And because a rate can be quoted more than one way, it helps to know how nominal and effective rates differ.
These examples assume the same return every year, which no real investment delivers. They show how fees behave, not what any product will earn, and nothing here is financial advice.