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Next: run the fee arithmetic yourself
The compounding calculator lets you change the growth rate, the fee and the years, and shows how a small yearly drag changes the end balance.
What is included
- What it is, in plain words
- The formula or mechanism, with exact arithmetic
- How it hits grid, martingale and DCA bots
- A check you can run before you switch a bot on
Who it is for
- People who run or plan to run a trading bot
- Anyone reading a backtest or a bot sales page
- Readers who want the numbers, not the pitch
- Not advice, and not a signal service
Key facts
- A robo advisor is a service that builds a portfolio for you from a questionnaire, then rebalances it. It usually holds broad funds and charges a percent of the assets each year.
- A trading bot follows rules that open and close trades. It often uses leverage, trades over short periods and can lose far more than a fee.
- In the made-up example below, $10,000 growing 6 percent a year for 20 years ends at $32,071 with no fee and $26,231 with a 1 percent yearly fee. The fee removes $5,840 (calculated by us on 30 Oct 2026, exact).
- Rules about protection, licensing and complaints differ by country. Check the rules where you live before using either one.
- Neither removes market risk. Falling prices lower the value of a robo advisor portfolio as well. See drawdown.
Three things that get mixed up
A robo advisor
A robo advisor is an online service that picks a mix of investments for you. You answer a questionnaire about your age, goals and comfort with losses. The service maps your answers to a model portfolio, usually a spread of broad funds across shares and bonds. It then keeps that mix on target by rebalancing, which is explained below. It normally charges a percent of your balance each year, sometimes plus the running cost of the funds inside.
A trading bot
A trading bot is a program that follows rules to open and close trades. The rules might be a price level, an indicator or a grid of orders. It can trade many times a day, and it often trades with borrowed money. See trading robot for how these programs are built, and DCA bot for one that buys a fixed amount on a schedule.
An AI trading tool
An AI trading tool uses a model to find patterns or to suggest or place trades. The model changes the way signals are made, but it is still a trading tool. It still needs rules for size and exit, and it can still lose. See AI trading software and AI trading platform.
Side by side
This table describes the usual pattern. Individual services differ, so read the terms of the one you are looking at.
| Robo advisor | Trading bot | AI trading tool | |
|---|---|---|---|
| What it does | Builds a fund portfolio and rebalances it | Opens and closes trades by fixed rules | Uses a model to find or place trades |
| Who sets the rules | The provider, from your questionnaire | You, or the bot maker | The model and its maker, often hard to see |
| How it is paid | Usually a percent of assets each year | Subscription, one-off price, or fees per trade | Subscription or a share of results, varies |
| What it can lose | The fall in the funds, plus the fee | The fall in the trades, possibly more than the deposit if leveraged | Same as a trading bot |
| How often it trades | Rarely, mostly when rebalancing or when you add money | From many times a day to a few times a year | Varies |
| What you can test | Little: the model portfolio and its fees can be read, not backtested as a bot | Backtest, forward test and paper trade the rules | Hard: the model may change and may not be open to test |
How fees compound
A percent fee sounds small. It is charged on the whole balance every year, including the growth you earned, so it also removes the growth that money would have produced later. Over long periods the gap is larger than the fee rate suggests.
Here is a made-up example. Start with $10,000. Assume it grows a constant 6 percent a year before any fee, which real markets do not do. Then compare two cases: no fee, and a flat 1 percent of the balance taken at the end of each year. Calculated by us on 30 Oct 2026, exact.
| Year | No fee | With 1 percent fee | Gap |
|---|---|---|---|
| 5 | $13,382 | $12,726 | $656 |
| 10 | $17,908 | $16,196 | $1,712 |
| 15 | $23,966 | $20,612 | $3,354 |
| 20 | $32,071 | $26,231 | $5,840 |
After 20 years the no-fee balance is $32,071 and the fee balance is $26,231. The fee took $5,840, which is 18.2 percent of the no-fee ending balance, from a fee rate of only 1 percent. This is the same arithmetic as in the compounding calculator: a small yearly drag grows into a large gap. These figures are made up. They say nothing about what any real service returns or charges.
The same logic applies to a trading bot. Subscription fees, spreads and commissions are a drag on every period. A bot that trades often pays more of them than a service that rarely trades.
Rebalancing, explained
Rebalancing means selling a little of what has grown and buying a little of what has lagged, to return to the target mix. Suppose a made-up portfolio targets 60 percent shares and 40 percent bonds, starting at $10,000. Over a year the shares rise 20 percent and the bonds do not move. Calculated by us on 30 Oct 2026, exact.
| Step | Shares | Bonds | Total | Share weight |
|---|---|---|---|---|
| Start | $6,000 | $4,000 | $10,000 | 60.0% |
| After a year | $7,200 | $4,000 | $11,200 | 64.3% |
| After rebalancing | $6,720 | $4,480 | $11,200 | 60.0% |
The shares drifted to 64.3 percent of the portfolio, so a rebalance sells $480 of shares and buys the same amount of bonds. The aim is to keep the risk level you chose, not to raise returns. A bot that adds to a falling position does something different. It changes risk by trade size, and that can compound losses. See DCA strategy for the buy-on-a-schedule idea.
Where protection and rules differ
Whether a provider must be licensed, how client money is held, whether any compensation scheme covers a failure, and how complaints are handled all depend on the country and on the type of service. A trading bot sold as software is usually not regulated in the way a managed portfolio is. A leveraged account carries its own rules. Do not assume the protections you know from one country apply in another, and do not assume a service has any. Look up your own regulator and read the terms of the provider.
Limits
- Market risk stays. If the funds fall 30 percent, the portfolio falls close to 30 percent. A rebalance does not prevent that. Read about drawdown to see how a fall and the climb back differ.
- A questionnaire is a rough guide. It cannot know how you will react in a bad year.
- Fees are certain, returns are not. The fee is taken in every year. Growth is not.
- A bot has an edge or it does not. Whether a rule set has positive expectancy can be tested. Whether a model portfolio will do well cannot be proven in advance.
- Bet size matters most in a bot. See the Kelly criterion for how sizing relates to growth and ruin.
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FAQ
Frequently Asked Questions
What is a robo advisor?
A robo advisor is an online service that builds a portfolio from your questionnaire answers and rebalances it. It usually holds broad funds and charges a percent of your assets each year.
Is a robo advisor the same as a trading bot?
No. A robo advisor maintains a mix of funds and trades rarely. A trading bot follows rules to open and close trades, sometimes many times a day and sometimes with leverage.
How do fees affect a robo advisor over time?
The fee is charged on the whole balance every year, so it also removes later growth. In a made-up example, a 1 percent yearly fee cost $5,840 of $32,071 over 20 years.
Can a robo advisor lose money?
Yes. Its portfolio follows the funds it holds, so a fall in those markets lowers the balance, and the fee is charged on top.
Is a robo advisor regulated?
It depends on the country and the service. Licensing, how assets are held and any compensation scheme vary, so check your own regulator and the terms of the provider.
Are the numbers on this page real?
Example numbers are made up to show how the maths works, and the page says so. A figure only counts as exact when the page says it was calculated on a stated date. Nothing you enter in a calculator leaves your browser.
Can I use this to decide whether to run a bot?
It can show whether a bot's numbers hold together and how much an account can lose. It cannot say what the market will do, and it is not advice. Use it to ask better questions, then read the terms of your own broker or exchange.
Is this financial advice?
No. It is general education. All numbers are made up, and your situation, fees and rules will differ.
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