A volatility stop places the protective stop a multiple of Average True Range away from the entry or a structural level, rather than at an arbitrary fixed percentage or dollar amount. The logic: a stock's own recent range is the best estimate of the "noise" the position must tolerate before the thesis is actually wrong. A high-volatility name gets a wider stop (so normal swings don't eject you); a quiet name gets a tighter one. The core tension is that the multiple itself is discretionary — too tight and you get whipsawed out by noise, too wide and each loss is large — so the method removes the arbitrariness of the distance but not the judgment about how much room is enough.

How it's calculated / formed

ATR is J. Welles Wilder's volatility measure from New Concepts in Technical Trading Systems (1978). It is built in two steps:

1. True Range (TR) — the greatest of: (a) current High − current Low, (b) |current High − previous Close|, (c) |current Low − previous Close|. The previous-close terms capture gaps and limit moves a plain high-low range would miss. 2. ATR — Wilder's smoothing (a smoothed/modified moving average, not a simple SMA) of TR. The standard period is 14. The recursive form is:

Current ATR = [(Prior ATR × 13) + Current TR] / 14

The seed is a simple average of the first 14 TR values. Wilder's 14-period smoothing is roughly equivalent to a ~27-period EMA (≈ 2n−1), so ATR reacts slowly and persistently — important, because a stop built on it won't flap on a single wild bar.

The stop itself: stop = reference price − (M × ATR) for a long (above the reference for a short), where M is the multiplier. M of roughly 1.5–3× ATR is a commonly cited convention range rather than a derived optimum — the right value depends on the stock, timeframe, and how much whipsaw the trader will accept.

How it's used in practice

Three canonical deployments:

• Fixed initial stop. At entry, set the stop M×ATR below the entry or below the structural level (swing low, breakout base). The position then has a noise-aware fixed risk for the trade.
• Chandelier Exit (the canonical ATR trailing stop). Developed by Charles ("Chuck") Le Beau, it anchors to the highest high since entry and trails up as price rises:

- Long: Chandelier Exit = Highest High (n) − ATR(n) × multiplier - Short: Chandelier Exit = Lowest Low (n) + ATR(n) × multiplier - StockCharts' defaults are 22 periods and a 3.0 multiplier ((22, 3.0)). The stop ratchets up (long) as new highs form or ATR contracts, and never moves down — it locks in gains while still giving the trend its volatility-sized leash.

• Feeding position size. This is the most decision-useful link for swing trading. The ATR stop fixes the per-share risk = M × ATR. Combined with a fixed account-risk budget (e.g. risk X% of equity per trade), shares = (account $ risk) ÷ (M × ATR). Volatile names → wider stop → fewer shares; quiet names → tighter stop → more shares — so risk-per-trade stays constant across very different instruments. (See Volatility-Based Sizing.)

StockCharts' own guidance: volatile stocks may need a higher multiplier to cut whipsaws; dull stocks a lower one to stay sensitive — i.e. the multiple is tuned, not fixed.

Strengths & limitations

Strengths. Adapts the stop to each instrument's actual volatility instead of a one-size-fits-all percent; reduces noise-driven stop-outs on jumpy names; quantifies risk per share, which plugs directly into sizing; the trailing form (Chandelier) is rules-based and monotonic (won't loosen on you).

Limitations — stated honestly:

• The multiple is discretionary. There is no universally optimal value; 1.5–3× is convention, not law. Optimizing M on past data risks curve-fitting.
• Wide stops in volatile regimes. When ATR expands (crashes, earnings runs), the stop sits far away — meaning either a large dollar loss if hit, or a forced reduction in size that shrinks the position's upside.
• Lagging input. Wilder smoothing means ATR adjusts slowly; after a sudden volatility spike the stop may be sized off pre-spike conditions.
• Still a mechanical level. An ATR stop is a calculable price; it can be run/hunted like any visible level, and a clean ATR distance can still slice through meaningful support/resistance that a structure-aware stop would have respected.
• #1 misuse: treating a single multiplier as a fixed rule across all stocks and regimes, instead of tuning it to volatility and pairing it with structure.

System relevance

This node is the volatility approach to stop placement; pair it with Structure-Based Stops (swing lows, support, pattern invalidation), which use chart geometry rather than a derived distance — many traders combine them (place at structure, then widen to at least M×ATR so noise can't eject the trade). It is the input side of Volatility-Based Sizing (the ATR stop distance is what converts a risk budget into a share count). For the indicator-side mechanics of ATR and related gauges, cross-link (TA) Volatility Indicators. Augustus should consume an ATR stop as a risk-distance input that simultaneously bounds the position size — and should flag, not silently accept, cases where the ATR-implied stop is so wide it forces an uneconomically small position or sits beyond key structure.

Sources

• StockCharts ChartSchool — Average True Range (ATR) (Wilder 1978; TR definition; [(Prior ATR × 13) + Current TR] / 14; 14-period default; volatility-not-direction).
• StockCharts ChartSchool — Chandelier Exit (Charles Le Beau; long/short formulas; (22, 3.0) defaults; multiplier guidance for volatile vs dull stocks).
• StockCharts ChartSchool — ATR Trailing Stops.
• Macroption — ATR Calculation Methods and Formulas (Wilder smoothing ≈ EMA of period 2n−1).
• J. Welles Wilder, New Concepts in Technical Trading Systems (1978) — original ATR.