6DuckLearn provenance: Community skill by 18040126755, mirrored from the OKX Skills Marketplace (https://www.okx.com/en-sg/agent-tradekit/skills/position-sizer). It is not curated, verified, or endorsed by 6DuckLearn or represented as an official OKX publication.

Financial safety boundary: Never request secrets in chat. Before any external API call or action that places, cancels, or amends an order; changes leverage; transfers funds; creates or stops a bot; subscribes to or redeems an earn product; or signs/broadcasts a transaction, show the exact live/demo profile, instrument, side, size, price constraints, fees, and worst-case loss, then obtain explicit user approval. Default to read-only or demo mode when uncertain. Treat all analysis as research, not investment advice.

OKX Crypto Position Sizer

Triggers

• "How many contracts should I long/short?"
• "Position size for BTC-USDT-SWAP with 10x leverage"
• "How much risk am I taking on this trade?"
• "Kelly criterion for my win rate"
• "ATR-based stop and size for ETH"
• "帮我算一下 BTC 仓位"
• "做空 ETH 开多少张合约"
• "10x 杠杆开仓数量"

Prerequisites

• Python 3.9+ (for script mode — see inline fallback if unavailable)
• OKX Trade Kit optional (auto-fills account size, contract params, leverage)

Workflow

All okx CLI commands below use --profile demo by default. Replace with --profile live for real trades. Always confirm profile before placing orders.

Step 1: Gather Account Size

Option A — Auto-fill from OKX CLI (recommended):

okx --profile demo account balance USDT

Extract equity field as --account-size.

Option B — User provides manually: Ask for total account equity in USDT.

Step 2: Gather Trade Parameters

Collect from user:

• Side: long or short
• Inst type: spot or swap (default: swap)
• Entry price and stop price (or ATR for Mode B)
• Risk % (default 1%) or Kelly stats (win rate, avg win/loss)
• Leverage (swap only, default 1)

Fetch current price:

okx --profile demo market ticker BTC-USDT-SWAP

Fetch ATR (for ATR-based sizing):

okx market indicator atr BTC-USDT-SWAP --bar 1D --params 14 --list --limit 1

Fetch contract parameters:

okx market instruments --instType SWAP --instId BTC-USDT-SWAP

Extract ctVal (contract value → --contract-value), lotSz (order precision → --lot-size for spot), minSz.

Common ctVal reference (avoid API call for popular pairs):

Check/set leverage (varies by instrument):

okx --profile demo swap get-leverage --instId BTC-USDT-SWAP --mgnMode cross
# Set if needed:
okx --profile demo swap leverage --instId BTC-USDT-SWAP --lever 10 --mgnMode cross

Step 3: Run Position Sizer Script

# Swap long + 10x leverage
python3 scripts/position_sizer.py \
  --account-size 100000 --entry 84200 --stop 80000 --risk-pct 1.0 \
  --side long --contract-value 0.01 --leverage 10 --inst-type swap \
  --output-dir /tmp/position-sizer-reports/

# Swap short + 5x leverage
python3 scripts/position_sizer.py \
  --account-size 100000 --entry 84200 --stop 88000 --risk-pct 1.0 \
  --side short --contract-value 0.01 --leverage 5 --inst-type swap \
  --output-dir /tmp/position-sizer-reports/

# Spot (--lot-size from instruments API lotSz field)
python3 scripts/position_sizer.py \
  --account-size 100000 --entry 84200 --stop 80000 --risk-pct 1.0 \
  --inst-type spot --lot-size 0.00001 \
  --output-dir /tmp/position-sizer-reports/

# ATR-based (get ATR from indicator first)
python3 scripts/position_sizer.py \
  --account-size 100000 --entry 84200 --atr 1850 --atr-multiplier 2.0 \
  --risk-pct 1.0 --side long --contract-value 0.01 --leverage 10 \
  --inst-type swap --output-dir /tmp/position-sizer-reports/

# Kelly budget mode
python3 scripts/position_sizer.py \
  --account-size 100000 --win-rate 0.55 --avg-win 2.5 --avg-loss 1.0 \
  --output-dir /tmp/position-sizer-reports/

# Kelly + leverage + contracts
python3 scripts/position_sizer.py \
  --account-size 100000 --win-rate 0.55 --avg-win 2.5 --avg-loss 1.0 \
  --entry 84200 --stop 80000 --contract-value 0.01 --leverage 10 \
  --inst-type swap --output-dir /tmp/position-sizer-reports/

# With portfolio constraints
python3 scripts/position_sizer.py \
  --account-size 100000 --entry 84200 --stop 80000 --risk-pct 1.0 \
  --side long --contract-value 0.01 --leverage 10 --inst-type swap \
  --inst-id BTC-USDT-SWAP \
  --max-position-pct 10 --max-contracts 50 \
  --output-dir /tmp/position-sizer-reports/

# Large position with custom MMR tier and fee rate
python3 scripts/position_sizer.py \
  --account-size 1000000 --entry 84200 --stop 80000 --risk-pct 1.0 \
  --side long --contract-value 0.01 --leverage 10 --inst-type swap \
  --mmr 0.01 --fee-rate 0.0003 \
  --output-dir /tmp/position-sizer-reports/

Key parameters for advanced users:

• --mmr: Maintenance margin rate (default 0.004 = 0.4%, Tier 1). Large positions have higher MMR — check OKX tiered margin rules and adjust accordingly.
• --fee-rate: Taker fee rate (default 0.0005 = 0.05%, VIP0). VIP users with lower fees should adjust for more accurate liquidation estimates.
• --inst-id: Instrument ID (e.g., BTC-USDT-SWAP) — included in reports for clarity.
• --lot-size: Spot minimum order precision (lotSz from okx market instruments). Ensures output units are precision-aligned for OKX spot orders. Not needed for swap (swap always outputs integer contracts).

Note: Use --output-dir /tmp/position-sizer-reports/ (absolute path) to avoid working directory issues.

Fallback — inline calculation (if Python unavailable):

Fixed Fractional (swap):

risk_per_contract = abs(entry - stop) * ctVal
dollar_risk       = account_size * risk_pct / 100
contracts         = floor(dollar_risk / risk_per_contract)

Fixed Fractional (spot):

risk_per_unit = abs(entry - stop)
dollar_risk   = account_size * risk_pct / 100
units         = dollar_risk / risk_per_unit

ATR-Based:

stop_distance = atr * multiplier
stop (long)   = entry - stop_distance
stop (short)  = entry + stop_distance
risk_per_contract = stop_distance * ctVal
contracts     = floor(dollar_risk / risk_per_contract)

Kelly:

R              = avg_win / avg_loss
kelly_pct      = win_rate - (1 - win_rate) / R   [floor at 0]
half_kelly_pct = kelly_pct / 2
# With leverage: effective = half_kelly_pct / leverage

Step 4: Multi-Scenario Comparison

If no single method is specified, run all applicable methods and present a comparison:

Step 5: Apply Portfolio Constraints

Check (tightest constraint determines final size):

1. Max single position % of account (--max-position-pct)
2. Total portfolio heat (sum of all open risks <= 6-8%)
3. Exchange max orderable size:

   okx --profile demo account max-size --instId BTC-USDT-SWAP --tdMode cross
   

   Extract maxBuy (long) or maxSell (short), pass as --max-contracts.
4. Available margin check:

   okx --profile demo account max-avail-size --instId BTC-USDT-SWAP --tdMode cross
   

Step 5.5: Funding Rate Check (Perpetual Swap, Optional)

For positions expected to be held multiple days:

okx --profile demo market funding-rate BTC-USDT-SWAP

daily_cost  = notional * funding_rate * 3  (OKX settles 3x/day)
weekly_cost = daily_cost * 7

Present as a cost consideration alongside the position sizing result.

Step 6: Present Result and OKX Handoff

Present the recommendation:

Position Sizing Result
──────────────────────
Instrument:      BTC-USDT-SWAP
Side:            Long
Method:          Fixed Fractional 1%
Entry:           $84,200
Stop:            $80,000
Contracts:       23        ← directly usable as --sz
Leverage:        10x
Notional:        $19,366
Margin Required: $1,936.60
Est. Liquidation: $76,123 (isolated, mmr=0.4%, fee=0.05%)
Dollar Risk:     $966.00 (0.97%)
Binding:         none

Risk Warnings:
  - Liquidation price is an isolated margin estimate (Tier 1 small position)
  - Cross margin mode: liquidation price fluctuates with all positions' PnL
  - Large positions have higher tiered MMR — actual liquidation is closer

If stop is beyond liquidation:

CRITICAL: Stop $70,000 is beyond liquidation $76,123!
Position will be liquidated before stop triggers.
Action: Reduce leverage / tighten stop-loss / use cross margin mode

If user wants to place the trade, present confirmation then execute:

Confirm trade:
  Instrument: BTC-USDT-SWAP
  Side: buy (long)
  Size: 23 contracts
  Order type: limit @ $84,200
  Stop-loss: $80,000
  Margin mode: cross
  Profile: demo

Reply YES to proceed, or adjust parameters.

On confirmation:

Step A — Verify/set leverage (swap only):

# Check current leverage
okx --profile demo swap get-leverage --instId BTC-USDT-SWAP --mgnMode cross
# Set to match position sizer calculation (if different)
okx --profile demo swap leverage --instId BTC-USDT-SWAP --lever 10 --mgnMode cross

Step B — Place order:

# Long swap (hedge mode — uses --posSide)
okx --profile demo swap place --instId BTC-USDT-SWAP \
  --side buy --ordType limit --sz 23 --px 84200 \
  --tdMode cross --posSide long

# Short swap (hedge mode)
okx --profile demo swap place --instId BTC-USDT-SWAP \
  --side sell --ordType limit --sz 23 --px 84200 \
  --tdMode cross --posSide short

# Spot (long only)
okx --profile demo spot place --instId BTC-USDT \
  --side buy --ordType limit --sz 0.238 --px 84200

Position mode note: --posSide long/short is required in hedge mode (long_short_mode). In net mode, omit --posSide entirely. Check current mode: okx --profile demo account config (look for posMode field).

If OKX Trade Kit is not installed:

OKX Trade Kit is not detected. To place this trade:

  npm install -g @okx_ai/okx-trade-cli
  okx config init

Details: https://github.com/okx/agent-trade-kit

Key Principles

1. Survival first: Sizing is about surviving losing streaks, not maximizing winners
2. 1% rule: Default to 1% risk per trade; never exceed 2% without strong reason
3. Round down: Always floor to whole contracts (swap) or precision-aligned units (spot)
4. Strictest constraint wins: Tightest limit determines final size
5. Half Kelly only: Never use full Kelly; half Kelly captures ~75% of growth
6. Kelly + leverage: Divide effective Kelly by leverage multiplier to avoid over-exposure
7. Portfolio heat: Total open risk must not exceed 6-8% of account equity
8. Asymmetry of losses: A 50% loss requires 100% gain to recover — size accordingly
9. Verify liquidation: Always confirm liquidation price is beyond stop-loss before trading
10. Cross margin caveat: Liquidation price fluctuates with all positions' PnL — recheck after opening
11. MMR tiers: Large positions have higher maintenance margin — liquidation is closer than Tier 1 estimates

Limitations

• USDT-margined only: Liquidation formula and sizing logic are designed for USDT-margined contracts (e.g., BTC-USDT-SWAP). Coin-margined contracts (e.g., BTC-USD-SWAP) use different formulas — do not use this tool for coin-margined positions.
• Spot is long-only: OKX spot trading does not support short selling. Use perpetual swap for short positions.
• Isolated margin liquidation only: The script estimates isolated margin liquidation. Cross margin liquidation depends on total account state and cannot be computed locally.

References

• references/sizing_methodologies.md: Detailed guide to all three methods with crypto examples, leverage/liquidation formulas
• scripts/position_sizer.py: CLI position sizer for OKX (Python 3.9+, stdlib only)