Combined Risk Across Open Positions: One Budget for the Whole Book

The answer first: add the risk, then check it against one number

Sizing a single trade asks what one stop-out costs. Running several at once asks a different question: what does it cost if they all stop out. That number is the sum, and it has to be measured against a budget you set for the whole book, not per trade. Asked as a portfolio risk calculator — how much of this account is committed, and how much room is left — it is the same two lines below.

Here is a 25,000 USD account with four JPY crosses open, each one sized on its own to 1% of the balance, and a book cap of 3%:

Four trades that each looked like 1% are 3.97% together. Against a 3% book cap of 750.00 USD, this book is over its limit by 241.33 USD — and nothing in the platform will say so, because nothing in the platform adds risk up.

Why the sum is the right number, and correlation does not change it

Two things get mixed together here, and keeping them apart makes the rest easy.

• The sum is the worst case. If every stop is hit, the loss is 991.33 USD whatever the correlation is. Correlation does not shrink the worst case; it only changes how likely the worst case is.
• Correlation decides whether that worst case is remote or ordinary. Four unrelated markets rarely stop out in the same hour. Four JPY crosses go the same way on the same JPY move, so the "everything hits at once" scenario is not a tail event — it is the normal way this book loses.

So the rule is: always add the risk, and treat the sum as the realistic outcome when the positions share a currency. The sum is the conservative figure and, on a clustered book, the honest one.

The seven pairs that are one bet

Every pair quoted in JPY puts that currency on the same side of your trade: long EUR/JPY is long EUR and short JPY, long AUD/JPY is long AUD and short JPY. Four different-looking tickets, one direction. This is the site's own reference data for that group:

Seven symbols, one shared quote currency, and identical pip size, contract size and unit step. That uniformity is useful for the arithmetic — every one of them converts at the same JPY rate and rounds at the same 1,000-unit step — and it is exactly what makes the risk stack: a JPY move that reaches one stop is already halfway to the other six.

The same grouping exists on the other side. EUR/USD, EUR/GBP and EUR/JPY are three tickets and one EUR view. If your book has four crosses and they share two currencies between them, count the currencies, not the tickets.

Sizing the fourth trade against what is left

The fix is not to shrink all four. It is to check the book before the last ticket and size that one against the remainder. With a 3% cap of 750.00 USD, the first three trades already use 741.33 USD:

1. Book cap: 25,000 × 3% = 750.00 USD, which is 112,500 JPY at 150.00.
2. Open risk from the first three: 37,200 + 37,200 + 36,800 = 111,200 JPY = 741.33 USD.
3. Room left: 112,500 − 111,200 = 1,300 JPY = 8.67 USD.
4. AUD/JPY has a 0.50 stop distance, so 1,300 ÷ 0.50 = 2,600 units, rounded down to the 1,000-unit step = 2,000 units.
5. That position risks 2,000 × 0.50 = 1,000 JPY = 6.67 USD. The book total becomes 112,200 JPY = 748.00 USD, inside the cap.

2,000 units is 0.02 lots, and a 0.02-lot trade is not really a trade — it is a rounding artefact with a commission attached. The honest reading of the arithmetic is that the fourth idea does not fit this book, and the choice is between skipping it, closing something else first, or accepting a smaller cap on the other three.

Gross exposure tells a different story from risk

Four positions risking 3.97% carry a lot more than 3.97% of the account in notional terms. Same four tickets, valued at their entry prices and converted at 150.00:

The book is 269,760 USD of gross exposure on a 25,000 USD account — more than ten times the balance — while risking just under 4% of it. At 30:1 that is 8,992.00 USD of margin, about 36% of the balance, which is why margin never raises a flag here: the leverage check passes comfortably at the same moment the risk check fails.

Exposure and risk answer different questions and both are worth capping. Exposure is what a gap costs you; risk is what a stop-out costs you. A per-symbol exposure limit, say 200% of balance on any one instrument, would already have cut the USD/JPY ticket from 93,000 to 50,000 units. Whether you want that limit depends on whether your stops hold — the leverage and margin guide covers where the exposure figure comes from.

Three caps, and which one binds

A single per-trade percentage is one constraint. A book that runs several positions needs three, applied in this order:

• Per trade: 1% of balance — 250.00 USD here. This is what sizes the individual ticket.
• Per currency bloc: 1.5% of balance — 375.00 USD shared by everything quoted in, or exposed to, one currency. Applied to the JPY group, the first trade takes 248.00 USD and leaves 127.00 USD for the rest: the second ticket is cut to 31,000 units risking 124.00 USD, and the group total is 372.00 USD. Trades three and four get nothing.
• Whole book: 3% of balance — 750.00 USD across everything open, whatever the direction.

Whichever of the three produces the smaller size is the one that applies. In this example the bloc cap is the binding one, and it binds long before the book cap does — which is the point of having it. Four trades across four different currency blocs would get close to the book cap; four trades across one bloc hit the wall at the second ticket.

The percentage you pick for each level comes out of how long a losing run you can sit through, which is what the risk per trade page works through, and the streak tables behind it.

Where to look before the next ticket

• Add the open risk yourself, in your account currency, before you click — the platform shows margin and floating profit, not risk.
• Count the tickets that share a currency, not the tickets. Seven JPY pairs are one bet wearing seven names.
• Check the exposure on the largest single position against a per-symbol limit as well as the risk.
• Recompute after every stop move. Pulling one stop closer frees budget for the next trade; widening one eats it.
• Recompute again after a winner closes. The released budget is real, and it is the cheapest source of room you have.

The cap no broker will enforce for you

Margin is the only aggregated number a platform computes, and it is computed against leverage, not against your stop distances. A book can sit at 36% margin used with 4% of risk stacked in one direction and show no warning of any kind. Bloc limits, per-symbol exposure limits and book-level risk limits exist only if you write them down and check them by hand.

That is a small amount of arithmetic to do on a phone before a click, and it is the difference between four trades and one oversized bet on a single currency. Add the risk, compare it with the cap, and let the smaller number decide the size.

Open the position size calculator

Questions traders ask

The sum, which is 3.97% on the example here rather than anything close to 1%. Nothing in a trading platform adds risk across open tickets, so that number only exists if you work it out before the last order goes in.

No. If every stop is hit the loss is 991.33 USD whatever the correlation is — correlation changes how likely that scenario is, not how large it is. On a book of JPY crosses, everything stopping out together is the ordinary outcome, not a tail event.

Because they share a currency. Every pair quoted in JPY puts yen on the same side of the trade, so a JPY move that reaches one stop is already halfway to the other six. Count currencies rather than tickets.

Against what is left, not against the full per-trade figure. With a 750.00 cap and 741.33 already open, the fourth ticket has 8.67 USD of room, which buys 2,000 units of AUD/JPY. A 0.02-lot position with commission attached is a rounding artefact, not a trade.

Because the two answer different questions. The book here carries 269,760 USD of notional on a 25,000 USD account while risking under 4%, needing only about 36% of the balance in margin at 30:1. The margin check passes at exactly the moment the risk check fails.

It depends which one you mean. In trading, the phrase usually means what this page does: add up what every open ticket would cost if each stop were hit, then compare the total with a cap you set for the book. In investment management the same words often mean a volatility statistic computed from a covariance matrix — a different quantity with a different purpose. This page does the first one, and it deliberately does not adjust for correlation: the sum is the loss you are exposed to, and counting currencies rather than tickets is how it accounts for concentration.

Related guides

• Forex risk calculator — add up what is open right now: total money at risk, share of equity, and the net currency bet.
• Adding to a position — the same one-budget rule applied to several entries into a single trade.
• How much should you risk per trade? — where the per-trade and book percentages come from.
• Position size by instrument — contract size, pip size and unit step for all 131 symbols.
• Leverage, margin and position size — why the margin figure stays green while the risk figure is over the line.
• Position size after spread and commission — the cost side of each of these tickets.
• Stock correlation calculator — how closely two of these tickets actually move together, which is the number this page deliberately does not adjust for.