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SIZING

Every way to specify the size of a BUY or SELL order. Sizing is the single mandatory field on entry actions (unless DEFAULTS.sizing is set).

The forms available today

Form Meaning
SIZING <number> Fixed lots / units
SIZING <pct> PCT OF EQUITY Percentage of total equity (cash + open P&L)
SIZING <pct> PCT OF BALANCE Percentage of cash balance only
SIZING <usd> USD Fixed USD notional value
SIZING POSITION.<stream> The full current position quantity (for closes/scaling)

Coming in Phase 24

SIZING N PCT RISK — size the position so a stop-out costs exactly N% of equity — is planned but not yet shipped. See Planned features for the workaround.

Fixed quantity

BUY btc SIZING 0.1

Buys 0.1 of whatever the venue's unit is. For Bybit spot BTC, that's 0.1 BTC. For MT5 EURUSD, that's 0.1 lots = 10,000 units of base currency.

When to use: prototyping, simple strategies, when the venue's lot size aligns with your risk budget at known prices.

Gotcha: doesn't scale with account size. A 0.1 lots size on a $1,000 account is risky; on $100,000 it's tiny. Use percent-based sizing for portable strategies.

Percent of equity

BUY btc SIZING 5.0 PCT OF EQUITY

Sizes the position at 5% of ACCOUNT.equity. If equity is $10,000, the order is sized to represent $500 of position value (at current price).

Variants:

SIZING 5.0 PCT OF EQUITY    -- 5% of equity (includes open P&L)
SIZING 10 PCT OF BALANCE    -- 10% of cash balance only (ignores open P&L)

The difference matters when you have unrealized P&L: EQUITY includes it (the size scales with open profit/loss), BALANCE doesn't.

When to use: position sizing that scales with account performance. Good for compounding strategies.

Fixed USD notional

BUY btc SIZING 1000 USD

Sizes the position to represent exactly $1000 of notional value (at current price). For BTC at $50k, that's 0.02 BTC. For BTC at $60k, that's 0.01666… BTC.

When to use: consistent dollar exposure across symbols of different price levels. "I want $1000 of BTC and $1000 of EUR regardless of how each is priced."

Position-based (for partial closes)

SELL btc SIZING POSITION.btc

Sells exactly the current position size — equivalent to CLOSE btc. Mostly used in scale-out logic:

SELL btc SIZING POSITION.btc * 0.5     -- partial close: 50% of position

You can multiply, divide, or do any arithmetic on POSITION.<stream>.

Computing risk-based size manually (Phase 24 workaround)

Until SIZING N PCT RISK ships, the same effect is achievable with USD sizing and a LET expression:

LET stopDist = atr(btc, 14) * 2
LET riskUsd  = ACCOUNT.equity * 0.01           # 1% of equity at risk
LET riskQty  = riskUsd / stopDist              # size that loses riskUsd if stop hits

RULES
    WHEN ema(btc.close, 9) CROSSES ABOVE ema(btc.close, 21)
    THEN BUY btc SIZING riskQty
         BRACKET { STOP_LOSS AT btc.close - stopDist, TAKE_PROFIT AT btc.close + stopDist * 3 }

This produces the same behaviour as SIZING 1.0 PCT RISK will once Phase 24 lands — you compute the size from equity_at_risk / stop_distance yourself. Not as elegant, but works today.

Defaults via DEFAULTS

If most of your strategies use the same sizing, hoist it:

DEFAULTS {
  sizing = 0.1
}

RULES
    WHEN ... THEN BUY btc     -- inherits sizing = 0.1

Multiple sizings per stack

A STACK (pyramid) carries one SIZING for the seed layer, but you can override per layer in the layer-list form:

BUY btc STACK [
  0.05,                       -- seed: 0.05 lots
  0.10 AT entry + 200,        -- layer 2: 0.10 lots at +200
  0.15 AT entry + 400         -- layer 3: 0.15 lots at +400
]
BRACKET { ... }

See STACK.

Common gotchas

  • Sizing is required. Either on the action or via DEFAULTS.sizing. Both missing = parse error.
  • Percent-of-equity ignores stop distance. A 5% position with a tight stop loses very little; with a wide stop loses a lot. Use the manual workaround above to factor in the stop.
  • Broker minimum sizes. MT5 brokers enforce a minimum lot (volumeMin) and step (volumeStep). If your computed size is below the minimum, the order rejects.
  • Whole-number lots on some venues. Futures often require integer contracts. A computed size of 0.327 will round (typically down) or reject. Check your venue's specs.
  • Sizing units are venue-side. A "size of 0.1" means 0.1 of the venue's unit (lots, contracts, base currency) — not 0.1 USD or 0.1% of anything.

What this composes with

  • Actions — SIZING is a modifier on BUY / SELL
  • BRACKET — pair sizing with STOP_LOSS/TAKE_PROFIT
  • LET — name a sizing computation for reuse
  • DEFAULTS — set a default sizing for the whole strategy
  • Planned features — PCT RISK and what's coming