What Is Options Margin?
Options margin is the cash or securities that a trader must deposit with their broker as collateral when writing (selling) options contracts. Unlike buying options — where the maximum loss is limited to the premium paid — selling options exposes the writer to potentially large losses. Brokers require margin to ensure the seller can cover those obligations. The margin requirement is set by exchange rules (primarily the CBOE and OCC) and may be increased by individual brokers.
Our free Options Margin Calculator uses standard CBOE Reg-T margin formulas to estimate the initial margin, maintenance margin, and buying power reduction for naked calls, naked puts, vertical spreads, short straddles, and short strangles. Simply enter a ticker, load the live options chain, select your strategy, and see the margin requirement for every available contract — all powered by real-time market data.
Why Use Our Options Margin Calculator?
CBOE Margin Formulas
Calculations follow standard Reg-T margin rules used by major U.S. brokers, including the 20% underlying price method and the 10% minimum for naked options.
Live Market Data
Option premiums, strike prices, implied volatility, and Greeks are fetched in real time so your margin estimates reflect current market conditions.
Multiple Strategies
Calculate margin for naked calls, naked puts, bull call spreads, bear put spreads, short straddles, and short strangles — all from one tool.
Buying Power Insight
See exactly how much buying power each position will consume so you can size trades appropriately and avoid margin calls.
Risk Awareness
Understand maximum loss, net margin after premium, and whether a strategy has unlimited risk before you commit capital.
Compare Across Strikes
For naked options, view margin requirements for every strike in the chain side by side to find the best risk/reward trade-off.
How to Use This Options Margin Calculator
- 1
Enter a Ticker
Type any U.S. stock or ETF ticker (e.g., AAPL, SPY, TSLA, AMZN) and click "Load Options" to fetch the live options chain.
- 2
Choose a Strategy
Select from naked call, naked put, bull call spread, bear put spread, short straddle, or short strangle. The calculator adapts its interface to match the strategy.
- 3
Set Quantity & Filters
Adjust the number of contracts, expiration date, and strike price range to narrow the chain to the contracts you care about.
- 4
Review Margin Results
For naked options, the table shows initial margin, buying power reduction, premium received, and net margin for every contract. For spreads and straddles, select the specific legs and view a detailed margin summary card.
CBOE Options Margin Rules Explained
The margin formulas used in this calculator follow the standard Reg-T rules established by the CBOE and enforced by the OCC. Here is a summary of the key rules for each strategy type:
- Naked Call Margin: The greater of (a) 20% of the underlying stock price plus the option premium minus the out-of-the-money amount, or (b) 10% of the underlying stock price plus the option premium. This is multiplied by 100 shares per contract and the number of contracts.
- Naked Put Margin: The greater of (a) 20% of the underlying stock price plus the option premium minus the out-of-the-money amount, or (b) 10% of the strike price plus the option premium. The maximum loss on a naked put is limited to the strike price times 100.
- Vertical Spread Margin: For debit spreads (bull call, bear put), the margin equals the net debit paid. For credit spreads, the margin equals the width of the spread (difference between strikes) times 100 per contract.
- Short Straddle / Strangle Margin: The margin on the higher-margin leg plus the full premium of the other leg. Because both sides carry risk, the combined margin is significantly higher than a single naked option.
Note that individual brokers may impose higher "house" margin requirements. Portfolio margin accounts may have different (often lower) requirements based on risk-based models. This calculator provides Reg-T estimates as a baseline reference.