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Portfolio cost calculator: what it actually costs you to hold
Short answer
Six things quietly take money out of a portfolio every year: commissions, the bid-ask spread, currency conversion, interest your broker keeps on your cash, fund fees, and platform charges. Every one of them is disclosed somewhere and almost nobody adds them up. This calculator adds them up, converts the total into basis points, and shows what that total costs you over a decade.
Annual cost of holding
Nothing is sent anywhere, nothing is stored, no account. Leave a field at zero if it does not apply to you.
The last two fields measure cash drag: interest your broker earns on your idle balance and does not pass to you. It is the least visible cost on this page and often the largest.
What it costs over ten years. Same portfolio, same seven percent gross return, with and without the annual cost above. The gap is not the fees you paid, it is the fees plus everything they would have earned.
Assumes the portfolio is held for ten years with no contributions and a constant cost rate. It is an illustration of scale, not a forecast.
The spread cost assumes you cross half the quoted spread on each execution, which is the standard convention. Change any figure and everything recalculates.
Why almost nobody builds this
Not because it is technically difficult. Every input is a number you already have. The reason is that the sites best placed to build it are paid by brokers, and a tool whose main output is your broker is expensive is not a tool a broker affiliate wants ranking on its own domain.
We are paid by a research platform, not by brokers, which removes that particular conflict from this particular page. It does not remove every conflict, and how we are paid is set out in full at how we make money. This page carries no commercial links of any kind.
The six costs, and where each one hides
Commissions
The only cost most people can name, and usually the smallest. A flat charge per execution, sometimes a percentage with a minimum. It matters at small trade sizes and stops mattering quickly as they grow: a one dollar charge on a two hundred dollar trade is fifty basis points, and on a five thousand dollar trade it is two.
The bid-ask spread
The gap between what buyers offer and sellers ask. You cross roughly half of it on every execution, and unlike a commission it never appears on a statement, which is why zero commission brokers can advertise honestly while still being expensive. On liquid large companies it is fractions of a basis point. On small companies, thin ETFs, or anything traded outside its home market hours, it can be far larger than any commission you were worried about.
Currency conversion
The one that catches people who invest internationally. A half percent conversion fee on ten thousand dollars is fifty dollars, and it is charged on the way in and again on the way out. Brokers vary enormously here, from a few basis points on a genuine spot rate to well over one percent on a marked-up rate presented as free. Our page on where broker costs actually hide covers the marked-up rate problem in detail, and the Interactive Brokers fee breakdown works through one specific example.
Cash drag
The least visible line on this page and frequently the largest. Your broker earns the prevailing rate on your idle cash and passes on some fraction of it, or none. On three thousand dollars sitting uninvested, the difference between four percent and half a percent is a hundred and five dollars a year, which is more than most people pay in commissions. It appears on no statement because it is not a charge, it is an absence.
Fund fees
Deducted daily inside the fund, so the price you see is already net of them and no line ever appears. Use the weighted average across your holdings rather than the ratio of your largest position. If you are not sure what yours comes to, our expense ratio calculator works it out across a full portfolio.
Platform and custody charges
Common outside the United States and often the largest single item where they exist. Some brokers charge a percentage of assets, some a flat annual fee, some waive it above a threshold or if you trade a minimum number of times a quarter. Read the schedule rather than the summary page.
What a reasonable total looks like
There is no single right answer, because a portfolio of individual stocks held for years and a portfolio traded weekly are different problems. As rough orientation:
| Total annual cost | Reading |
|---|---|
| Under 30 bps | Efficient. Usually broad funds, low turnover, little or no currency conversion. |
| 30 to 75 bps | Normal for an active private investor with some international exposure. |
| 75 to 150 bps | Worth examining. Usually cash drag, conversion fees, or a platform charge doing the damage. |
| Over 150 bps | The costs are now a material part of your expected return, whatever the return turns out to be. |
For context, a mainstream index fund charges between three and twenty basis points a year, and that figure gets quoted constantly while everything else on this page gets quoted almost never. The point is not that costs are avoidable. It is that they are the only part of a portfolio's outcome you control completely.
Then there is the cost you choose
A research subscription is a fixed annual charge on top of everything above, which means it behaves like an expense ratio and gets cheaper in basis points as the portfolio grows. We test those platforms hands-on and publish what they cost against what they add.
Frequently asked questions
- What is a good total annual cost for a portfolio?
- Under thirty basis points is efficient and usually means broad funds with low turnover. Thirty to seventy five is normal for an active private investor with international holdings. Above one hundred and fifty basis points the costs become a material share of your expected return, and the usual culprits are cash drag, currency conversion and platform charges rather than commissions.
- Why does the calculator ask what interest my broker pays on cash?
- Because the difference between the prevailing rate and what your broker passes on is a real cost that appears on no statement. It is not a charge, it is an absence, which is exactly why it is so easy to miss. On a few thousand dollars of idle cash it frequently exceeds everything the same investor pays in commissions across a year.
- Is the bid-ask spread really a cost if I never see it?
- Yes. You buy at the ask and sell at the bid, so you cross roughly half the quoted spread on each execution. It never appears as a line item, which is why a zero commission broker can advertise truthfully and still be expensive. On liquid large companies it is negligible. On small companies and thin ETFs it is often larger than any commission.
- Does this include tax?
- No. Tax depends on your jurisdiction, your account type and your holding period, and any figure we produced would be wrong for most readers. Everything measured here is a cost charged or withheld by a broker, a fund or a platform, before tax enters the picture.
- Why show a ten year figure?
- Because an annual cost understates the damage. Money paid in fees is not only gone, it also does not compound, so the ten year gap is the fees plus everything those fees would have earned. The calculation assumes a constant portfolio, a constant cost rate and a seven percent gross return, and it is an illustration of scale rather than a forecast.
- Does this calculator store or send my figures anywhere?
- No. Everything runs in your browser, nothing is transmitted, nothing is saved and there is no account. Closing the tab discards the inputs.
Published 11 August 2026 by Jacob Shasha. This page carries no commercial links. Corrections are published at the correction log, and how this site is funded is set out at how we make money.