Daily and Weekly Risk Limits: Why Per Trade Is Not Enough
A per trade limit caps a single case and nothing else. It does not tell you what a bad day costs, because trades accumulate sequentially, and it does not tell you what a bad week costs, because positions also accumulate simultaneously. Only a three level structure helps, with its consequences written down in advance.
Why is a per trade limit not enough?
Because it makes a statement about one trade rather than about their sum. A trader capping risk per trade cleanly at one percent who takes six trades in a day has risked up to six percent that day without breaking a single rule.
That is the decisive point: a day with six losses is not a rule violation but the rule working as written, on a case it was never designed for. Which is exactly why such days feel so inexplicable afterwards.
Two routes lead to accumulation. Sequentially, as several trades happen one after another, and simultaneously, as several positions stay open in parallel. The first calls for daily and weekly limits, the second for a cap on open risk. The groundwork for the per trade calculation sits in position sizing and the one percent rule.
Which three levels do you need?
The daily limit
It caps what a single trading day is allowed to cost, calculated in R or as a percentage of the account. It is the most important of the three, because most expensive days develop within a few hours and a weekly limit arrives too late for them.
A sensible figure is a multiple of your per trade risk that still sits well below what you are willing to absorb in one day. Where exactly it sits gets derived below.
The weekly limit
It catches the case where several mediocre days add up without any of them reaching the daily limit. That case is less conspicuous than a single bad day and often more expensive in total.
What matters is that the weekly limit is smaller than five times the daily limit. Otherwise it is arithmetically unreachable and therefore has no effect.
Total open risk
This level concerns the present moment rather than the past: the sum of the distances between entry and stop across all open positions. It answers the question of what happens when everything moves against you at once.
It matters particularly when your positions share a theme and therefore move together. Why that happens more often than expected is covered under portfolio correlation.
How do you derive the numbers?
From the bottom up, starting from the decline you are willing to absorb rather than from the number of signals currently on your screen.
- Start with the weekly limit. Ask what decline within a single week still leaves you able to trade the following week unchanged.
- Derive the daily limit from it, as a fraction of the weekly figure. One day should not be able to fill the week on its own.
- Check against your per trade risk. The daily limit should be a small multiple of it, otherwise one of the two numbers does not fit.
- Set the open risk cap separately, because it has a different reference: it measures a state rather than a sum over time.
What counts as a normal decline over longer periods helps put these numbers in context, covered under trading drawdown.
Does the limit count gross or net?
This is the detail most implementations fail on, and it has to be answered in advance. The question is: does a gain refill your daily budget?
Counting net means a gain at midday can offset a loss from the morning, and you carry on as though nothing happened. That sounds fair but suspends the limit in exactly the situations it exists for, because an interim gain says nothing about whether your day is going well.
The more robust variant is therefore to count realised losses separately and not net them against gains. The limit then describes consumption rather than account balance.
Which variant you pick matters less than deciding once and writing it down. What does not work is deciding during the day, because that decision always comes out in favour of continuing.
What happens when a limit is reached?
Exactly what you wrote down beforehand and nothing else. Without a defined consequence, a limit is an observation rather than a rule.
Three consequences are common and hold up well, one per level:
- Daily limit reached: trading closes for the day, with no exception for an unusually good signal.
- Weekly limit reached: trading closes for the week, while existing positions continue to be managed as planned.
- Open risk reached: no new entry until room appears, either by trailing a stop or by closing a position.
The distinction between closing and not opening matters here. A reached daily or weekly limit does not require unwinding existing positions, since those have their own exit rules, covered under setting stop losses correctly. It requires opening no new ones.
Why must the consequence be fixed in advance?
Because it gets tested at the moment you are least willing to honour it. After three losses every signal looks like the chance to turn the day around, and that thought is what makes the rest of the day expensive.
A consequence written down in advance removes that decision from you. It is not made but read off, and that is the whole difference between a rule and a resolution.
A visible counter helps alongside it. A limit you have to work out in your head does not act at the decisive moment, because that is precisely when the arithmetic does not get done.
Do you need a monthly limit as well?
Usually not, for two reasons. The first is timing: a monthly limit arrives so late that the damage has already happened, while daily and weekly limits catch the accumulation where it actually forms.
The second is practical. A reached monthly limit locks you out for a long stretch, and long breaks are harder to sustain than short ones. A rule that gets broken when it counts is worse than a tighter one that holds.
A monthly view is therefore more useful as analysis than as a limit. At month end, look at how many days reached a limit and how consumption distributed across the weeks. That becomes the basis for reviewing your daily and weekly limits for the month ahead, outside trading hours rather than during them.
How does this differ from drawdown?
In timing and in effect. Drawdown measures an accumulated decline after the fact and describes where you stand. Daily and weekly limits act beforehand and determine how far it can go at all.
The two belong together but do not substitute for each other. Watching the decline alone gives you a metric and no brake. Setting limits without measuring the path leaves you unable to tell whether your limits match your own variability.
What do you record in your journal?
Three items, all cheap to maintain and all necessary if you want to check whether any of this works.
First, daily consumption per trading day in R, so you can see the distribution across weeks. Second, the number of days on which a limit was reached and what would have happened afterwards. Third, every case in which you traded past a limit, because the share of those cases is the real measure of success.
A trading journal fed by timestamps from an exchange connection supplies daily consumption automatically once risk per trade is recorded. The third item has to come from you and is the only one that costs effort.
What if a limit keeps getting broken?
Do not raise the limit, establish the cause. An occasional breach in the first weeks is normal, a regular one is a signal, and usually points to one of two causes.
Either the figure was set too low and does not match how you actually trade. In that case recalculate it once, in writing, outside trading hours. Or the limit is being treated as a recommendation rather than a rule, in which case the number is not the problem.
Both cases call for the same procedure: note the breach, finish the day or week as planned, and decide at the weekend with the numbers in front of you.