Definition and what it measures
Percentage drawdown is a risk metric that expresses the drop from a previous high (the “peak”) to a later lower value (the “trough”) in percentage terms. It answers: “From the highest level reached, how large is the decline relative to that highest level?”
In practice, the metric is usually computed from an account equity (or sometimes balance) series, where:
- Peak = the maximum equity observed up to a given time.
- Current value (trough point) = the equity at the time you measure drawdown.
- Drawdown (amount) = Peak − Current.
- Percentage drawdown = (Drawdown ÷ Peak) × 100.
This mechanics matters because the “peak” is path-dependent: the same current equity can imply different drawdown percentages depending on the history of earlier highs.
How the calculation works (mechanics)
Assume you have equity values recorded over time: E₀, E₁, E₂, … . At each time step, you identify the highest equity seen so far as the peak P, then compute the drawdown percentage from P to the current equity C.
Formula at a given time:
- Percentage Drawdown = ((P − C) / P) × 100
Key assumption to state explicitly:
- You are using the same equity definition consistently (e.g., equity including unrealized profit/loss if that’s what your data shows).
No market data is needed to understand the arithmetic; you only need a peak value and a later value.
Worked example with explicit assumptions
Assumptions (state once, use throughout)
- We track account equity (not margin, not balance) at four time points.
- Equity values are net of trading costs and fees as reflected in the equity series you are using.
- There is no change in the metric definition between time points (e.g., you do not switch from equity to balance mid-way).
Scenario values
Suppose equity is as follows:
- Time 1: C = 10,000 (this is the first peak)
- Time 2: C = 10,800 (new peak)
- Time 3: C = 10,200 (drawdown from the 10,800 peak)
- Time 4: C = 9,400 (larger drawdown from the same 10,800 peak)
Step-by-step calculations
At Time 3:
- Peak P = 10,800
- Current C = 10,200
- Drawdown amount = 10,800 − 10,200 = 600
- Percentage drawdown = (600 / 10,800) × 100 ≈ 5.56%
At Time 4:
- Peak P remains 10,800 (the highest equity so far)
- Current C = 9,400
- Drawdown amount = 10,800 − 9,400 = 1,400
- Percentage drawdown = (1,400 / 10,800) × 100 ≈ 12.96%
What this shows
- The drawdown percentage increases as equity moves farther below the earlier peak.
- It does not depend on how you got there; it only depends on the peak-to-current relationship.
Limitations and failure modes (what can go wrong)
- Wrong reference point (peak choice): If you compute the percentage drawdown using a peak that is not the maximum up to that date, the result is incorrect. Even small data mistakes (missing a prior high) can change the peak P and therefore the percentage.
- Metric mismatch (equity vs balance vs NAV): Different platforms or reports may show equity, balance, or net asset value with different components. Mixing definitions can make comparisons and verification unreliable.
- Costs and valuation timing: If your equity series reflects fees, spreads, swaps, or delayed valuation differently than you assume, then the computed drawdown from that series may not match your expectations. This is a failure mode of assumption alignment, not of the arithmetic.
- Path dependence and interpretation limits: Percentage drawdown summarizes “how far down from the peak,” not “how long you stayed down” or “how quickly you recovered.” Two sequences can share the same drawdown percentage but differ materially in duration.
Because of these limitations, historical drawdown metrics do not, by themselves, establish future outcomes.
Verification and next question you can answer
To independently verify a percentage drawdown number from any report or spreadsheet, you can check three items:
- Identify the peak value used for the calculation.
- Identify the current (trough) value at the measurement time.
- Confirm the formula: ((Peak − Current) / Peak) × 100.
If you want to deepen verification, a next useful step is to compare two metrics on the same equity series—one based on drawdown amount and one based on percentage—to see how normalization changes the interpretation.