N, ATR and Position Risk
How volatility-based risk links N, ATR, Unit sizing and stop distance in Turtle-style trading.
The Turtle method uses volatility to make risk more comparable across markets. A fixed number of contracts or coins does not mean the same thing in a calm market and a highly volatile market.
The role of N
N is a volatility measure related to Average True Range. It estimates how much a market typically moves over a given period. When N is larger, each unit of position carries more price risk. When N is smaller, the same nominal position may carry less price risk.
From volatility to position size
Position sizing usually starts with:
- account equity;
- allowed risk per Unit;
- N or ATR value;
- contract multiplier or instrument unit;
- stop distance.
The point is not to maximize size. The point is to make one trade’s risk understandable before entry.
Why this matters
Without volatility adjustment, the system may overtrade fast-moving markets and underuse calm markets. Volatility-based sizing helps normalize risk, though it does not remove gap risk, slippage or liquidity problems.