Black-Scholes Options Calculator

European call + put prices and the 5 Greeks (delta, gamma, vega, theta, rho) under the Black-Scholes-Merton model.

Inputs

Decimal year. 30 days โ‰ˆ 0.0822; 1 year = 1.0.

Implied or historical. S&P 500 ~15-20% historically; single stocks 25-40%; speculative ones higher.

Use 0 for non-dividend stocks; ~1.5-2% for S&P 500.

Result

Call / Put
$5.8836 / $8.5475
S=$100, K=$105, T=0.5000 yr, r=4.50%, ฯƒ=25.00%, q=0.00%.
  • Call price$5.8836
  • Put price$8.5475
  • dโ‚-0.06033
  • dโ‚‚-0.23711
  • N(dโ‚)0.47595
  • N(dโ‚‚)0.40629
  • โ€” Greeks (call) โ€”
  • Delta (call)ฮ” option price per $1 move in S.0.47595
  • Gammaฮ” delta per $1 move in S (same for call & put).0.022527
  • Vega (per 1% ฯƒ)ฮ” option price per 1 vol-point increase.0.28158
  • Theta (per day, call)Option-value decay per calendar day.-0.02443
  • Rho (per 1% rate, call)ฮ” option price per 1% rate increase.0.20855
  • โ€” Greeks (put) โ€”
  • Delta (put)-0.52405
  • Theta (per day, put)-0.01177
  • Rho (per 1% rate, put)-0.30476
  • Put-call parity checkShould be ~0 (numerical noise).|$-2.6639 โˆ’ $-2.6639| = $0

Step-by-step

  1. dโ‚ = [ln(S/K) + (r โˆ’ q + ฯƒยฒ/2)ยทT] / (ฯƒยทโˆšT) = -0.06033.
  2. dโ‚‚ = dโ‚ โˆ’ ฯƒยทโˆšT = -0.23711.
  3. Call = Sยทe^(โˆ’qยทT)ยทN(dโ‚) โˆ’ Kยทe^(โˆ’rยทT)ยทN(dโ‚‚) = $47.5946 โˆ’ $41.711 = $5.8836.
  4. Put = Kยทe^(โˆ’rยทT)ยทN(โˆ’dโ‚‚) โˆ’ Sยทe^(โˆ’qยทT)ยทN(โˆ’dโ‚) = $8.5475.

How to use this calculator

  • Enter S = current underlying price, K = strike price.
  • T = decimal years to expiry. 30 days = 30/365 = 0.0822.
  • r = annualized risk-free rate (use the 3-mo T-bill yield, ~5% in 2026).
  • ฯƒ = annualized volatility. Use historical (sample std dev ร— โˆš252) or implied from option chain.
  • q = continuous dividend yield. Use 0 for non-dividend stocks; ~1.5-2% for S&P 500.

About this calculator

The Black-Scholes-Merton model (Fischer Black, Myron Scholes, Robert Merton โ€” Nobel 1997 to Scholes & Merton; Black had died in 1995 and the prize is not awarded posthumously) prices a European-style option as the discounted risk-neutral expected payoff under a geometric-Brownian-motion stock-price process. The 5 standard Greeks measure first-order sensitivity to the inputs: ฮ” to underlying price, ฮ“ to delta itself, ฮฝ to volatility, ฮ˜ to time, ฯ to rate. The model assumes constant volatility (the most-violated assumption โ€” implied-vol smiles are exactly the market's correction), no early exercise, no transaction costs, and log-normally distributed prices. For US single-stock options (most are American-style), the European-style Black-Scholes price is a lower bound; the early-exercise premium is generally small for non-dividend-paying calls but can be material for puts and for calls on dividend-paying stocks just before ex-date.

Frequently asked

For European options, exactly. For American options, it's a lower bound โ€” early exercise can be optimal for puts (always) and for calls on dividend-paying stocks (just before ex-date). The premium is usually < 1% for non-dividend calls but can be 5-15% for ITM puts. Use binomial or finite-difference for American options when precision matters.

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