How Turtle position sizing works
A Unit is the slice of a position that a 1 N move turns into 1% of equity. The rules' heating oil example comes out at 16 contracts, and the calculator above starts on it.
The heating oil example, worked
The Turtles built positions in pieces they called Units, sized so that 1 N represented 1% of the account equity: Unit = 1% of account ÷ (N × dollars per point). N × dollars per point is the dollar volatility, what one contract makes or loses on a 1 N move.
- 1% of a $1,000,000 account is $10,000.
- Heating oil's N was 0.0141 and each contract was 42,000 dollars per point, so one contract moves 0.0141 × 42,000 = $592.20 per N.
- $10,000 ÷ $592.20 = 16.88, which the rules truncate to an even 16 contracts.
- 16 contracts × $592.20 = $9,475.20 per N, just under 1% of equity; the 2N stop puts $18,950.40 at risk, 1.90%.
The rules come from the Original Turtle Trading Rules, published free by the Original Turtles site and read on 29 October 2026. The PDF shows no author or year on its pages. Its example gives no price, so the calculator's 2.5 entry is ours; it only places the stop and the adds.
What N is
N is the 20-day average true range, the ATR under another name, in the market's own price units.
True range, the daily update, and the candles panel
True range is the largest of high − low, high − previous close and previous close − low. The rules define N as “the 20-day exponential moving average of the True Range, which is now more commonly known as the ATR”: each day N = (19 × previous N + true range) ÷ 20, started from a 20-day simple average of the true range.
That update is the smoothing Wilder used for his Average True Range, with 20 days in place of the usual 14. On TradingView the ATR indicator's default smoothing is RMA, Wilder's, with a default length of 14: set the length to 20 to read N there. Over a short history the starting average differs, and so can the last decimals.
The panel under the N field computes it for you: paste at least 21 daily rows of high, low and close. The first row only supplies a previous close, the next 20 give the true ranges whose average starts N, and each later row updates it. N is in the price's own units: dollars a gallon for heating oil, dollars per coin for Bitcoin, the quote itself (not pips) for a currency pair.
Stops and adding units
A 2N stop, an add every ½N, and one stop for the whole position that climbs ½N with each add. At 4 Units the loss if every stop is hit is 5N, not 8N.
The rules, the limits and the four-unit sum
Turtle stops sat 2N below the entry for longs and 2N above it for shorts. Since 1 N was 1% of equity, no trade risked more than 2%. Units were added at ½N intervals from the actual fill of the previous order, up to the limit; if the market moved quickly enough, all four Units in a single market could go on in a single day. Each time a unit was added, the stops for the earlier units were raised by ½N, so all the stops sat 2N from the most recently added unit.
Add up the loss if every stop is hit, unit by unit. At 4 Units the first unit is ½N from the stop, the second 1N, the third 1½N and the newest 2N: 5N, so 5% of equity at 1% per N before truncation, not 4 × 2% = 8%. In the heating oil example that is 5 × $9,475.20 = $47,376, 4.74% of $1,000,000, if each add fills exactly at its price.
| Level | Where | Most Units |
|---|---|---|
| 1 | Single market | 4 |
| 2 | Closely correlated markets | 6 |
| 3 | Loosely correlated markets | 10 |
| 4 | Single direction, long or short | 12 |
The Whipsaw alternative placed stops at ½N, for ½% account risk. The rules we quote don't say how whipsaw stops moved as units were added, so the calculator's whipsaw mode leaves each unit's ½N stop where it was placed: four Units then risk 4 × ½N = 2N.
Using it on crypto, futures and forex
The formula needs one fact about the market: what a 1.00 move pays on one contract, lot or coin.
Dollars per point, market by market
Futures. Dollars per point is the tick value ÷ the tick size: what one contract makes on a 1.00 move in its quote. The contract picker reads the point values in our futures tick value chart, where heating oil (HO) is $42,000 a point, the rules' figure; for a contract that isn't listed, type its point value. The Unit is truncated to whole contracts, as the rules do. For one stop on one contract, the futures position size calculator does the same arithmetic.
Crypto. For a coin priced in dollars, spot or a perpetual quoted per coin, one coin makes $1 on a $1 move, so dollars per point is 1 and the Unit comes out in coins. Pick the coin step your exchange allows, such as 0.001.
Forex and CFDs. Enter the value of a 1.0 move per lot. A 100,000-unit lot on a pair quoted in dollars makes $100,000 on a 1.0000 move; a CFD's contract size is on your broker's symbol specification. Round to the lot step, such as 0.01.
The arithmetic is the same everywhere. Whether a breakout system earns anything in a given market is a separate question: does turtle trading still work? takes it up, and the Donchian channel strategy covers the breakouts the Turtles' entries were built on.