$17.73 per barrel
That is the price of one quoted unit. By itself, it says nothing about how much one contract gains or loses.
Oil Was $17.73. Was Zero Really the Worst Case?
On April 20, 2020, the May WTI crude-oil futures contract opened at $17.73 per barrel. One standard contract represented 1,000 barrels. If you held one contract long at that price, a fall to zero would mean a $17,730 loss. The question is: was zero actually the floor?
- See why a low screen price can still create a large position risk.
- Turn a price move into the cash move for one contract.
- Work backward from a risk budget and an invalidation level to position size.
- Recognize when the minimum tradable unit makes zero the sensible size.
- Separate planned risk from the loss that is actually realized.
$17.73 looked cheap — but you were not holding one barrel
One standard WTI futures contract represented 1,000 barrels. So every $1 move in oil changed one contract's P/L by $1,000. The $17.73 quote was only the price of one barrel, not the maximum amount the position could lose.
You hold one standard May WTI futures contract long at $17.73 per barrel. One contract represents 1,000 barrels. If price keeps falling, what is the worst that can happen?
Choose the answer that matches your first instinct.
Oil moves $1. Why does the account move $1,000?
Because one standard contract bundled 1,000 barrels together. The screen showed “dollars per barrel”; the account felt the move across all 1,000 barrels. Position sizing starts by connecting those two numbers.
1 standard WTI = 1,000 barrels
A $1-per-barrel move therefore becomes a $1,000 move for one contract.
$17.73 × 1,000 = $17,730
That tells you the size of the market exposure. It does not mean the loss is capped at $17,730.
The threshold for holding the position
Margin helps determine whether the account can open and maintain the trade. It is not insurance against further losses.
Do not start with “How many contracts do I want?” Start with “Where would I stop believing the idea?”
Suppose you enter around $50 and your original reasoning no longer makes sense below $47.50. The $2.50 gap is the invalidation distance. It is the boundary that exists before position size is calculated — not a number you move around later just to fit more size.
- 1Set the risk budgetFor example, the trade is planned to risk no more than $600.
- 2Set the invalidation distanceFor example, entry to invalidation is $2.50 apart.
- 3See how large one unit really isIf one contract represents 100 units, then a $1 move changes one contract by $100.
- 4Only now calculate quantity$2.50 × 100 = $250 of planned risk per contract. $600 ÷ $250 = 2.4, so whole-contract sizing rounds down to 2.
Now turn the risk boundary into a position size
Zero was not a reliable price floor in the case above. Here, however, zero may be the correct position size.
A risk budget can be a fixed amount set in advance or an amount derived from account size and a per-trade risk limit. This example uses $600 for practice; it is not a universal amount or percentage. Start with standard WTI, then switch to a smaller contract.
Choose the size of one contract
Planned risk for 1 contract$2,000
Theoretical quantity0.3
Tradable quantity0
The planned risk for one contract is already above the budget, so the current tradable quantity is zero.
This exercise uses whole futures contracts. Real products are also affected by minimum trade size, spread, fees, slippage, FX conversion and liquidation rules.
If one minimum contract is already too large, position size is zero
Keep the $600 risk budget and use a $2 invalidation distance. A 1,000-barrel contract carries $2,000 of planned risk. The budget is only $600. In that case, the problem is not that you need to be braver — the product's minimum unit is simply too large for that risk budget.
| Contract | Size of one contract | Planned risk per contract | How many fit a $600 budget |
|---|---|---|---|
| Standard WTI | 1,000 barrels | $2,000 | 0 |
| E-mini WTI | 500 barrels | $1,000 | 0 |
| Micro WTI | 100 barrels | $200 | 3 |
Different contracts can track the same WTI market while representing very different amounts of oil. So the product name is not enough — you still need to know how large one tradable unit is. Use the latest official specification for the exact product.
Planning to lose $600 does not mean the final loss will be exactly $600
Position sizing can keep the plan within a chosen range before the order is placed. But the market does not promise to fill you at the exact price you had in mind. In fast markets, gaps or thin liquidity, the actual exit can be worse.
Price can jump past the level you wanted
You may want out at $47.50, but the next tradable price could already be $47 or lower.
Spread and fees still count
If the formula only uses price distance, the account can still pick up extra costs along the way.
The account may be forced to reduce sooner
If margin runs short or liquidation rules are triggered, the exit timing may not be entirely yours.
Find the boundary, check the product size, then calculate quantity
1
Where is the idea wrong?
Set the invalidation level and measure the distance from entry.
2
How large is one tradable unit?
Check contract size, point value or minimum trade size.
3
How much planned risk can the trade carry?
Divide the risk budget by planned risk per unit to get theoretical quantity.
4
Can that quantity actually be traded?
Round down to the allowed unit, then allow for spread, fees and slippage.
Put Your Understanding to the Test
Three quick checks: are you still confusing a low price with low risk?
Question 1 of 3
One contract represents 1,000 units. If price moves $2, how much does that contract move in cash terms?
Question 2 of 3
Risk budget is $600 and planned risk per contract is $250. Whole contracts only. How many fit?
Question 3 of 3
Why can a trade planned to lose $600 end up losing more?
Let Mira run the position-size math with you
Give Mira a risk budget, invalidation distance and the number of units in one product. It can check the planned risk per unit and the final quantity.
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Put this concept into practice
Position Sizing: Risk First, Then Quantity
Calculate position size from account size, risk-per-trade percentage, and stop distance, and explain how position size amplifies both profit and loss.
Consistent Position Size Is What Lets You See Strategy Performance
Understand that if position size changes with mood on every trade, the resulting P/L already has the sizing decision mixed in, making it impossible to cleanly judge the strategy itself; position sizing is part of the strategy, and the key is a consistent, predefined sizing/risk-budget rule — not mechanically keeping share count or notional amount the same. 1% is just an example risk budget.