Advanced QuantLesson 1
Options Pricing & The Greeks
Understand how options are priced and the five Greeks that measure different dimensions of risk.
14 minute read
5 key takeaways
Options Pricing: The Foundation
Options are priced according to the Black-Scholes model, which uses five inputs to determine fair value. Understanding these is essential for algorithmic options trading.
Black-Scholes Formula
C = S×N(d₁) - K×e^(-rT)×N(d₂)
Where d₁ and d₂ are complex functions of S, K, r, T, and σ
The five inputs:
- S = Current stock price
- K = Strike price
- T = Time to expiration (in years)
- r = Risk-free rate
- σ = Implied volatility (the market's guess of future volatility)
The Five Greeks
| Greek | Measures | Range | Trading Use |
|---|---|---|---|
| Delta (Δ) | Price change per $1 move in stock | Call: 0-1, Put: -1-0 | Directional exposure |
| Gamma (Γ) | Rate of delta change | 0 to Max at ATM | Options: gamma risk |
| Theta (Θ) | Daily time decay | Negative for buyers | Expect daily loss for long options |
| Vega (ν) | Sensitivity to implied volatility | Positive for long | Bet on volatility changes |
| Rho (ρ) | Sensitivity to interest rates | Usually small | Less important for trading |
python
from scipy.stats import norm
import numpy as np
def black_scholes(S, K, T, r, sigma):
d1 = (np.log(S/K) + (r + 0.5*sigma**2)*T) / (sigma * np.sqrt(T))
d2 = d1 - sigma * np.sqrt(T)
call_price = S * norm.cdf(d1) - K * np.exp(-r*T) * norm.cdf(d2)
delta = norm.cdf(d1)
gamma = norm.pdf(d1) / (S * sigma * np.sqrt(T))
vega = S * norm.pdf(d1) * np.sqrt(T) / 100 # Per 1% change in vol
theta = (-S * norm.pdf(d1) * sigma / (2*np.sqrt(T)) - r*K*np.exp(-r*T)*norm.cdf(d2)) / 365
return call_price, delta, gamma, vega, theta
# Example: AAPL $150 call, stock at $148
S, K, T, r, sigma = 148, 150, 30/365, 0.05, 0.25
price, delta, gamma, vega, theta = black_scholes(S, K, T, r, sigma)
print(f"Call price: ${price:.2f}")
print(f"Delta: {delta:.3f} (price moves $0.72 if stock moves $1)")
print(f"Gamma: {gamma:.4f} (delta changes by this much if stock moves $1)")
print(f"Vega: {vega:.2f} (price changes $0.23 if IV changes 1%)")
print(f"Theta: ${theta:.3f} (loses $0.02 per day from time decay)")IV Rank & IV Percentile
Implied Volatility (IV) at this very moment—where does it sit in its 52-week range?
- IV Rank > 50: Options are expensive relative to history
- IV Rank < 50: Options are cheap relative to history
- Buy options when IV Rank < 30 (cheap)
- Sell options when IV Rank > 70 (expensive)
Portfolio Greeks
Your portfolio delta, gamma, theta, vega are the sums of your positions. Manage them as a portfolio, not individual options.
Practical Tip: Watch Theta Daily
For short options strategies (covered calls, sells), theta is your profit engine. Each day, time decay puts money in your pocket. Watch it daily to ensure decay is on your side.
Key Takeaways
- Black-Scholes model prices options based on 5 inputs
- Delta measures price sensitivity
- Gamma measures delta sensitivity
- Theta is time decay (friend to sellers, enemy to buyers)
- Vega measures volatility sensitivity