Most traders open a trade based on gut feeling — putting in a random amount without any calculation.
This is gambling.
Professional traders calculate their exact position size before every single trade. It takes 30 seconds and completely transforms your risk management.
Position Size = Risk Amount ÷ Stop Loss Distance
That is it. Three inputs. One calculation. Complete position size.
Risk Amount
Your account size × your risk percentage.
$10,000 account × 2% risk = $200 risk amount.
Stop Loss Distance
The difference between your entry price and your stop loss price.
Entry: $80,000. Stop: $77,000. Distance = $3,000.
Position Size
$200 ÷ $3,000 = 0.0667 Bitcoin
At the planned stop price, the unrounded quantity risks $200, or 2% of the account, before fees and slippage. A stop order does not guarantee that execution price; losses can exceed the planned amount.
Example 1 — Bitcoin trade:
Account: $10,000
Risk: 1% = $100
Entry: $80,000
Stop loss: $78,500
Stop distance: $1,500
Position size: $100 ÷ $1,500 = 0.0667 BTC
Dollar value of position: 0.0667 × $80,000 = $5,336
Example 2 — Ethereum trade:
Account: $5,000
Risk: 2% = $100
Entry: $3,000
Stop loss: $2,800
Stop distance: $200
Position size: $100 ÷ $200 = 0.5 ETH
Dollar value of position: 0.5 × $3,000 = $1,500
Example 3 — Small altcoin:
Account: $10,000
Risk: 1% = $100
Entry: $0.50
Stop loss: $0.42
Stop distance: $0.08
Position size: $100 ÷ $0.08 = 1,250 coins
Dollar value: 1,250 × $0.50 = $625
The stop loss distance dramatically affects position size.
Same risk — different stops:
Account: $10,000. Risk: 1% = $100.
Tight stop — $500 distance:
Position size = $100 ÷ $500 = 0.2 BTC
Dollar position = $16,000 at an assumed $80,000 entry.
This is notional exposure, not the planned $100 loss. It exceeds a $10,000 unleveraged cash account; reduce the position or use a different feasible setup rather than assuming sufficient buying power.
Wide stop — $5,000 distance:
Position size = $100 ÷ $5,000 = 0.02 BTC
Dollar position = $1,600
Key insight:
Tighter stop = larger position size.
Wider stop = smaller position size.
Risk in dollars remains the same — $100.
For a fixed dollar-risk budget, a tighter stop produces a larger calculated position, not a smaller one. An unrealistically tight stop can be triggered by normal price movement. Choose a justified stop, then size within available capital, liquidity and execution limits.
Leverage changes the margin required, not the risk-based quantity formula. Funding, fees, slippage and liquidation rules must also be considered.
10x leverage example:
Account: $10,000
Risk: 1% = $100
Entry: $80,000
Stop loss: $79,200
Stop distance: $800
Without leverage:
Position size = $100 ÷ $800 = 0.125 BTC = $10,000 position
With 10x leverage:
You only need $1,000 margin to control $10,000 position.
The planned price-move loss is $100 only if the stop fills at the assumed price. Fees, funding, slippage or liquidation can increase it.
Warning:
Leverage amplifies both gains AND losses.
A small adverse move can trigger liquidation.
For beginners — avoid leverage entirely.
No leverage multiple is automatically safe; margin and liquidation rules vary by product and exchange.
Before every trade ask:
If you cannot answer all four — do not enter the trade.
Many free calculators exist online. But understanding the formula manually is essential — so you know what the calculator is doing and can verify results.
Bookmark this formula:
Position Size = (Account × Risk%) ÷ Stop Distance
In the next topic we will study leverage in detail — one of the most dangerous and most misunderstood tools in crypto trading.