Options Selection: Strike, Expiry & Strategy Choice

Options Selection: Strike, Expiry & Strategy Choice

Selecting a stock is only half the job when trading options. You then face a matrix of thousands of contracts — dozens of strikes across dozens of expiration dates. Algorithms navigate this matrix systematically using Greeks, implied volatility, and a defined strategy framework.

Step 1 — Read the Market Outlook

Before touching a strike or expiry, the algorithm classifies the market outlook for that stock into one of five regimes. The regime dictates which strategy structure is appropriate.

Step 2 — Select the Strike Using Delta

Delta measures how much the option price moves per $1 move in the stock. It also approximates the probability that the option expires in-the-money. Algorithms use delta as the primary strike selector because it normalizes across stocks regardless of price level.

def select_strike(chain, target_delta, option_type='call'):
    """Pick the strike closest to target_delta from the options chain."""
    best = None
    best_diff = float('inf')

    for contract in chain:
        if contract.option_type != option_type:
            continue
        diff = abs(abs(contract.delta) - target_delta)
        if diff < best_diff:
            best_diff = diff
            best = contract

    return best

# Examples:
# Directional long call → target_delta = 0.40
# Short put for income  → target_delta = 0.20 (sell 20-delta put)
# Iron condor short leg → target_delta = 0.16 on each side

Step 3 — Select the Expiry Using DTE

Days To Expiry (DTE) controls the trade-off between time decay speed and risk. Shorter expiry = faster theta decay but more gamma risk (price swings hit harder). Longer expiry = slower decay but more time for the thesis to work.

Step 4 — Check IV Rank Before Deciding to Buy or Sell Premium

Implied Volatility Rank (IVR) compares current IV to its 52-week range. This single number determines whether the algorithm should buy or sell options premium.