vulcan-lot-size-calculator

vulcan-lot-size-calculator

Use this skill for:

• Converting a desired token amount to base lots before placing an order
• Converting a USD notional to base lots when you need lot-level precision
• Understanding why lot sizes differ per market

Why This Matters

Vulcan's size field is in base lots, not tokens or USD. Getting this wrong means trading 100x more or less than intended.

For market orders, prefer tokens or notional_usdc when you do not need lot-level control. Use this skill when passing size, placing limit orders, or checking exact lot math.

Step-by-Step Calculation

Step 1: Fetch market info

vulcan_market_info → { symbol: "SOL" }

Extract base_lots_decimals from the response.

Step 2: Convert tokens to base lots

base_lots = desired_tokens * 10^base_lots_decimals

Step 3: Pass base lots to trade tool

vulcan_trade → { symbol: "SOL", side: "buy", order_type: "market", size: <base_lots>, acknowledged: true }

Market-order shortcut:

vulcan_trade → { symbol: "SOL", side: "buy", order_type: "market", tokens: 0.5, acknowledged: true }
vulcan_trade → { symbol: "SOL", side: "buy", order_type: "market", notional_usdc: 100, acknowledged: true }

Worked Examples

SOL (base_lots_decimals = 2)

Want	Calculation	Base lots
0.1 SOL	0.1 * 10^2 = 0.1 * 100	10
0.5 SOL	0.5 * 100	50
1 SOL	1 * 100	100
5 SOL	5 * 100	500

BTC (base_lots_decimals = 4)

Want	Calculation	Base lots
0.001 BTC	0.001 * 10^4 = 0.001 * 10000	10
0.01 BTC	0.01 * 10000	100
0.1 BTC	0.1 * 10000	1000

ETH (base_lots_decimals = 3)

Want	Calculation	Base lots
0.01 ETH	0.01 * 10^3 = 0.01 * 1000	10
0.1 ETH	0.1 * 1000	100
1 ETH	1 * 1000	1000

Converting from USD Notional

To trade a specific USD amount via base lots:

1. Get current price: vulcan_market_ticker → { symbol }
2. Calculate tokens: desired_tokens = usd_amount / mark_price
3. Calculate base lots: base_lots = desired_tokens * 10^base_lots_decimals

Example: $100 worth of SOL at $150/SOL, decimals=2:

tokens = 100 / 150 = 0.6667
base_lots = 0.6667 * 100 = 66.67 → round to 67

For market orders, notional_usdc performs this sizing internally and quotes at current mid; actual fill can differ by spread and impact.

Common Mistakes

1. Passing token amount as size — If you want 0.5 SOL and pass size: 0.5, you'll get 0.005 SOL (0.5 base lots at decimals=2). Always multiply.

2. Using the wrong decimals — Each market has different base_lots_decimals. SOL=2, BTC=4, ETH=3. Always fetch fresh from vulcan_market_info.

3. Not rounding — Base lots must be whole numbers. Round to nearest integer after calculation.

4. Caching decimals across markets — Different markets have different decimals. Fetch per-market.