Start with one contract and a reproducible model
All calculations on this page use a hypothetical European option with strike K = $100, continuous risk-free rate r = 0%, continuous dividend yield q = 0%, and 365 calendar days per year. The baseline is spot S = $100, 30 days remaining and annualized IV = 20%. These are explicit teaching inputs, not retrieved quotes. Values are per share before contract scaling.
- Use the Black-Scholes model with continuous dividend yield: T = days / 365; d1 = [ln(S/K) + (r - q + σ²/2)T] / (σ√T); d2 = d1 - σ√T. Enter 20% IV as σ = 0.20 in these formulas.
- With N the standard normal cumulative distribution and φ(x) = exp(-x²/2) / √(2π), call price C = S exp(-qT)N(d1) - K exp(-rT)N(d2). Call delta = exp(-qT)N(d1); put delta = exp(-qT)[N(d1) - 1].
- Differentiating either delta with respect to S gives gamma Γ = exp(-qT)φ(d1) / (Sσ√T). Require S > 0, K > 0, T > 0 and σ > 0 for this expression. It is undefined at exactly zero time or volatility.
| Baseline output | Calculated value | Unit or meaning |
|---|---|---|
| Call price | $2.28715063 | Theoretical premium per share |
| Call delta | 0.51143575 | Option price change per $1 underlying move |
| Put delta | -0.48856425 | Negative first-order price sensitivity |
| Call and put gamma | 0.06954844 | Delta change per $1 underlying move |