Basics

Volatility

In one sentence

How much and how fast price moves - the measure that should set your stop distance, your position size, and whether a strategy fits an instrument at all.

Volatility is not risk. Risk is losing money; volatility is movement, and movement is what a trader is paid for. The mistake is keeping position size constant while volatility changes, so the same lot size risks three times as much in a stormy week as a calm one.

Tools like Average True Range exist to express volatility in price units, which is exactly what a stop needs.

The mistake it causes: fixed-pip stops. A 20-pip stop that is generous in August is noise in a central-bank week.

Volatility is not risk

Risk is losing money. Volatility is movement, and movement is what a trader is paid for. A market with no volatility offers no opportunity at any level of skill. The mistake is not trading volatile instruments; it is keeping position size constant while volatility changes.

Why fixed stops fail

A 20-pip stop is generous in a quiet August week and pure noise during a central bank month. The same number produces wildly different probabilities of being hit depending on conditions you never checked. Average True Range exists precisely to express volatility in price units, which is exactly what a stop needs.

ConditionATRSensible stopPosition size
QuietLowTighterLarger
NormalAverageStandardStandard
Event weekHighWiderSmaller

Note that the money at risk is identical in all three rows. That is the whole point of sizing from the stop rather than from habit.

Volatility clusters

Quiet periods follow quiet periods and violent periods follow violent ones. This is one of the most robust statistical features of financial markets, and it has a practical consequence: the day after a huge move is more likely to be large than a random day, so stops and sizes set during calm need revisiting.

What to do with this

  • Scale stop distance with a volatility measure rather than using a fixed number.
  • Let position size absorb the change so risk stays constant.
  • Expect volatility to persist after a spike, not to immediately normalise.

Related terms

Position sizing Choosing how large a trade to take so that hitting your stop loss costs a fixed, small, pre-decided percentage of the account. Stop loss A resting order that closes a position once price reaches a level where your trade idea is proven wrong. Drawdown The fall from an account peak to its lowest point before a new peak - and the measure of what you must be able to sit through to keep a strategy.

This term is explained in context in the primer .

More in Basics: Spread, Leverage, Margin, Liquidity.

Education only, not financial advice. Trading is high risk and most retail accounts lose money.