Most traders can state how much they're risking on any single open position. Far fewer can state, with a concrete number, how much they're risking across all open positions combined at this exact moment — a figure sometimes called "portfolio heat." This gap matters most precisely when it's least visible: multiple positions that each look individually reasonable can combine into a dangerously concentrated total risk. Here's the concept at three levels of depth.
Beginner Level: Calculating Total Portfolio Heat
Portfolio heat, in its simplest concrete form, is the sum of the dollar risk across every currently open position, expressed as a percentage of total account value.
- Concrete calculation: for each open position, calculate (entry price − stop-loss price) × number of shares = dollar risk on that position. Sum this figure across all open positions, then divide by total account value.
- A common beginner-level guideline: keeping total portfolio heat under roughly 6-8% of account value at any given time, even if individual positions are each within an acceptable per-trade risk limit.
- The beginner-level insight: five positions each risking 2% individually sum to 10% total account risk if all five were to hit their stops simultaneously — a number that can be easy to lose track of when evaluating positions one at a time rather than in aggregate.
Intermediate Level: Adjusting for Correlation Between Positions
Simple portfolio heat treats every position as independent, but positions in the same sector, or otherwise historically correlated, don't actually move independently — they tend to hit their stops together during a correlated move, not separately.
| Concept | Concrete Application |
|---|
| Correlation-adjusted heat | Group open positions by sector or historical price correlation; sum the heat within each correlated group separately, not just as one flat total |
| Effective concentrated risk | A correlated group's combined heat represents the risk that could materialize from a single shared catalyst — treat this grouped figure, not just the flat total, as the real concentration risk |
| Concrete guideline | Cap any single correlated group's combined heat at roughly the same limit used for an individual position's per-trade risk cap (commonly 2-3% of account value), even if the flat, unadjusted total across all positions looks acceptable |
Advanced Level: Dynamic Heat Limits Based on Market Regime
At the advanced level, the maximum acceptable portfolio heat itself becomes a variable adjusted to current market conditions, rather than a single fixed percentage used at all times.
Concrete Advanced Adjustments
- Reduce maximum total heat during high-volatility regimes — if standard practice allows up to 8% total heat during calm markets, cutting that ceiling to roughly 4-5% during confirmed high-volatility periods accounts for the wider stop distances and larger potential losses per position during those stretches.
- Track realized heat versus planned heat over time — comparing the portfolio heat calculated at position entry against what was actually realized when positions closed reveals whether stops are being honored as planned or if actual losses are systematically running larger than the calculated heat assumed.
- Set a hard total-heat circuit breaker — a specific, absolute maximum total heat percentage (for example, 12-15%) beyond which no new positions are opened regardless of how attractive an individual setup looks, preventing a string of good-looking individual trades from compounding into an unacceptable aggregate risk.
The Takeaway
Portfolio heat scales from a simple sum-of-individual-risks calculation at the beginner level, to a correlation-adjusted figure that accounts for positions moving together at the intermediate level, to a dynamically-capped figure that adjusts for current market regime at the advanced level. The common thread at every level is the same: individual position risk, however carefully sized, doesn't tell you your actual total exposure — only an explicit aggregate calculation does.
This post is educational content for traders and not financial advice. Portfolio heat calculations reduce but do not eliminate risk, including the risk of correlated positions moving against you simultaneously. Trade with capital you can afford to lose.
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