How many credit spread contracts can I sell with my available buying power?

How this is calculated

• Margin required per contract equals the strike width minus the net credit received, multiplied by 100 shares per contract. This is the standard Reg T margin requirement most brokers use for a defined-risk vertical credit spread.
• Maximum contracts equals your available buying power divided by the margin required per contract, rounded down to a whole contract.
• This is the same number as the spread's maximum possible loss per contract, since a credit spread's max loss and margin requirement are the same calculation under standard rules.
• Broker-specific requirements can differ, especially for accounts with pattern day trader margin, portfolio margin, or additional house requirements. Some brokers also add a small buffer on top of the standard requirement.
• This tool sizes the trade to your buying power. It does not check whether that many contracts fits your personal max risk-per-trade rule. Check that separately before placing the trade.