Portfolio Heat Calculator: Correlation-Adjusted Forex Risk

What is portfolio heat in forex trading?

Portfolio heat is the combined risk of every position you currently hold, expressed as a percentage of your account balance. A single trade risking 1% is easy to judge. Five open trades are not, because their risks do not simply add up when the pairs move together.

This tool reports two figures side by side:

• Naive Risk (Simple Sum) — adds up the stop-loss dollar risk of every position and divides by your balance. It assumes the positions are unrelated.
• Effective Risk (Correlation-Adjusted) — recomputes that total using the historical correlation between each pair of positions, so highly correlated same-direction trades are treated more like one larger trade.

The point is to expose hidden concentration. Three long trades on EUR/USD, GBP/USD and AUD/USD look like three separate bets but behave largely as one big short-dollar bet.

How do you use the Portfolio Heat Calculator?

1. Set your Account Balance (default $10,000) and your Max Heat % limit (default 6%) in the top bar.
2. In the Add Position form, choose a pair, direction (long or short), lot size, entry price and stop loss. Take profit is optional and only used to show the R:R column.
3. Each position is added to the Open Positions table with its individual percentage risk, dollar risk and reward-to-risk ratio.
4. Read the two heat gauges at the top: naive versus effective. The Currency Exposure panel shows your net long/short bias per currency, and the Correlation Warnings panel flags dangerous pairings.
5. Use the What-If Simulator to test a trade before opening it. It shows your naive and effective heat before and after, plus the change.

Positions, balance and limit are saved in your browser, and you can back up or import the portfolio as JSON.

How is correlation-adjusted heat calculated?

Each position's dollar risk is the stop distance in pips multiplied by pip value, where pip value = pip size × contract size × lots. For a standard lot (100,000 units) on a pair like EUR/USD that is $10 per pip.

Naive heat is the straight sum:

naiveHeat = (Σ dollarRisk) ÷ balance × 100

Effective heat aggregates the same dollar risks like portfolio volatility, weighting every pair of positions by their correlation:

effectiveHeat = √( ΣᵢΣⱼ riskᵢ · riskⱼ · corr(i,j) · dir ) ÷ balance × 100

Here corr(i,j) is the 1-day correlation between the two pairs (a position with itself is 1.0), and dir is +1 when both positions point the same way and −1 when they oppose. Opposite-direction trades therefore subtract risk, modelling a partial hedge. Because of the square root, two perfectly uncorrelated trades produce an effective heat below their naive sum, while two perfectly correlated same-direction trades produce an effective heat equal to it.

What do the heat levels and diversification score mean?

Both gauges are colour-coded against fixed thresholds applied to the percentage value:

If your effective heat exceeds your Max Heat limit, a red banner warns you are over the limit. Between 80% and 100% of the limit, a softer amber alert appears.

The Diversification Score is round((1 − average direction-adjusted correlation) × 100) across all position pairs, clamped to 0-100. Each pair contributes the absolute value of its correlation multiplied by +1 for same-direction or −1 for opposite-direction trades. A single position scores 100. A book of strongly correlated same-direction trades scores low (green at 60+, amber 30-59, red below 30). A Correlation Warning is raised whenever two positions have an effective correlation above 0.70 after accounting for direction.

Worked example: two correlated longs

Account balance $10,000. You open two positions, each 1.00 standard lot with a 20-pip stop:

• EUR/USD long — pip value = 0.0001 × 100,000 × 1.0 = $10/pip; risk = 20 × $10 = $200 (2.0%).
• GBP/USD long — same maths = $200 (2.0%).

Naive heat = ($200 + $200) ÷ $10,000 × 100 = 4.0% ($400), labelled Moderate.

Effective heat: the 1-day correlation between EUR/USD and GBP/USD is 0.86, same direction so dir = +1. The inner sum is 200² + 200² + 2(200 × 200 × 0.86) = 40,000 + 40,000 + 68,800 = 148,800. Its square root is $385.75, so effective heat = 385.75 ÷ 10,000 × 100 = 3.9% ($386), still Moderate.

Because both longs are short-dollar bets that move together, the correlation adjustment barely reduces the 4.0% sum — confirming these are nearly one trade, not two. The Diversification Score is round((1 − 0.86) × 100) = 14/100 (red), and a Correlation Warning fires because 0.86 exceeds 0.70.

Why correlated trades hide concentration risk

The danger portfolio heat exposes is hidden concentration: positions that look independent but are really one bet. Suppose you go long EUR/USD, GBP/USD and AUD/USD, each risking 1% of your account. A naive view says 3% total risk spread across three trades. In reality all three are short-dollar bets, so they tend to rise and fall together.

This matters in two opposite ways, and the tool models both:

• Day to day, because the pairs are highly correlated and pointing the same direction, the effective-heat formula keeps almost all of the combined risk rather than diversifying it away. Three correlated longs behave close to one larger position, not three smaller independent ones.
• During a dollar-driven event (an FOMC decision, a hot CPI print), all three can move against you at once and approach their stops together, so the full naive sum can become a real, simultaneous loss.

The takeaway: counting open trades tells you nothing about diversification. Only the correlation between them, and their direction, does.

The 6% portfolio-heat rule

A widely cited risk ceiling for open positions comes from Dr. Alexander Elder, who pairs a per-trade limit with a portfolio-wide limit in Trading for a Living:

• Per-trade limit: risk no more than about 2% of account equity on any single position.
• Total-heat limit: stop opening new trades for the rest of the month once your losses already realized this month plus the risk in all open positions together reach roughly 6% of equity.

The 6% figure is a guideline, not a law of markets. More conservative traders cap total open risk at 3-4%. The default Max Heat limit in this calculator is set to 6% for that reason, and you can change it to match your own drawdown tolerance. The key refinement the tool adds: your ceiling should apply to effective (correlation-adjusted) heat, not just the naive sum, because correlated same-direction trades concentrate risk that simple addition understates.

Reading your currency exposure

Every forex position is simultaneously long one currency and short another. Hold several positions and you can build a large directional bet on a single currency without noticing. The Currency Exposure panel nets this out across the eight currencies the tool tracks: USD, EUR, GBP, JPY, AUD, NZD, CAD and CHF.

For each position, the tool assigns its percentage risk to the two currencies involved. A long trade adds exposure to the base currency and subtracts it from the quote currency; a short trade does the reverse. Summing across all positions gives a net long (green) or short (red) figure per currency.

This is where the panel earns its place. You might think you hold five different trades, then see the chart report that all five are effectively short USD. That means one event — a single Fed announcement — moves your whole book the same way. Spotting a lopsided currency bar lets you rebalance before a scheduled event rather than after it.

What real diversification looks like in forex

Diversification is not about holding many pairs; it is about holding pairs that do not move together. Going long EUR/USD, EUR/GBP and EUR/JPY at the same time is not three diversified trades — it is one concentrated long-EUR bet, because EUR sits on the same side of all three.

Better diversification comes from mixing the base and quote currencies across your positions and favouring pairs with low correlation to each other. The tool's Diversification Score captures exactly this: it runs from 0 to 100 and is colour-coded green at 60 and above, amber from 30 to 59, and red below 30. A book of strongly correlated same-direction trades pushes the score down toward red; genuinely unrelated positions keep it high.

Hedging versus diversification

These two risk ideas are often confused, but they work differently:

• Diversification spreads risk across positions that have low correlation, so a loss on one is unlikely to coincide with a loss on another. It reduces the variability of the overall book without deliberately offsetting any single trade.
• Hedging deliberately takes an offsetting position to cancel some of the risk in a trade you already hold. The classic case is going long and short the same pair, which neutralises the directional exposure entirely.

The calculator reflects the hedging effect through direction. When two positions on correlated pairs point in opposite directions, the tool flips the sign of their correlation, so they partially offset and lower your effective heat. Same-direction correlated trades do the opposite and add to it. Hedging can cut risk, but it also caps the upside on the position it offsets, so it is a trade-off, not free protection.

Three ways to bring portfolio heat down

If your effective heat is above your Max Heat limit, you have three levers, roughly in order of impact:

1. Close positions, starting with the most correlated. The Correlation Warnings panel flags any two positions whose direction-adjusted correlation exceeds 0.70. Closing one side of a highly correlated same-direction pair usually cuts effective heat more than closing two unrelated positions.
2. Reduce lot sizes. Dollar risk scales directly with lots, so trimming size on your largest positions lowers both naive and effective heat proportionally.
3. Tighten stops. Moving a stop closer to entry shrinks the stop distance in pips and therefore the dollar risk — but only do this where price action justifies it, not purely to flatter the heat number.

Use the What-If Simulator before adding any new trade: it shows your naive and effective heat before and after the hypothetical position, so you can see whether it pushes you over your limit or adds correlation risk before you commit capital.

Frequently Asked Questions

• What is a safe portfolio heat level?

  This tool treats under 3% effective heat as Conservative, 3-5% as Moderate, 5-8% as Aggressive, and 8% or more as Dangerous. The built-in default Max Heat limit is 6%, with a warning once effective heat crosses it. Many risk-managed traders cap total open risk at 4-6%, but the right ceiling depends on your strategy and drawdown tolerance.

• What is the difference between naive and effective heat?

  Naive heat simply adds the stop-loss dollar risk of every open position and divides by your balance, assuming the trades are independent. Effective heat re-aggregates those same risks using each pair's 1-day correlation, so correlated same-direction trades count as more concentrated. The two numbers match when there is a single position or when all positions are perfectly correlated and same-direction; otherwise effective heat is lower.

• How does the calculator handle correlated currency pairs?

  It looks up the historical 1-day correlation between every pair of open positions and feeds it into the effective-heat formula. Same-direction trades use the correlation as-is; opposite-direction trades flip its sign, modelling a partial hedge. Any two positions whose direction-adjusted correlation exceeds 0.70 trigger a visible Correlation Warning so you can spot hidden concentration.

• How is the diversification score calculated?

  The score is round((1 − average direction-adjusted correlation) × 100), clamped between 0 and 100, measured across every pair of open positions. Each pair contributes the absolute value of its correlation multiplied by +1 for same-direction trades or −1 for opposite-direction trades. A single position scores 100. Strongly correlated same-direction trades push the average up and the score down. It is colour-coded green at 60 and above, amber from 30 to 59, and red below 30.

• Does this calculator use my real-time account or live prices?

  No. You enter the account balance, lot sizes, entry and stop prices manually, and risk is computed from those inputs using fixed pip values and stored historical correlations. Nothing is connected to a live broker feed or your real account. Positions and settings are saved only in your own browser and can be exported as a JSON backup.

• What inputs does each position need?

  Each position requires a pair, a direction (long or short), a lot size, an entry price and a stop loss. Take profit is optional; it is used only to display the reward-to-risk ratio and does not affect heat. Dollar risk is computed as the stop distance in pips multiplied by the pip value for that lot size.

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