Black-Scholes calculator (option price and Greeks)

Calculate European call and put prices and the Greeks (delta, gamma, theta, vega, rho) with the Black-Scholes-Merton model, including dividends.

更新于 已验证的示例:4

$
$
years
Days to expiry divided by 365 — you can type 30/365.
%
%
更多选项
%
试一试
Call price
$
Call price: $8.26
小数位数:2;取最近值,等距时取偶数末位
Put price
$5.79
Call delta
0.5909
Put delta
−0.4091
Gamma
0.02198
Call theta (per day)
−0.02578
Put theta (per day)
−0.01242
Vega (per 1% volatility)
0.2747
Call rho (per 1% rate)
0.2541
Put rho (per 1% rate)
−0.2335
d₁
0.229810
d₂
0.053033

The call is worth $8.26 and the put $5.79. For each 1.00 rise in the stock price the call gains about 0.5909, and with nothing else changing one day of time takes about 0.0258 off its value.

Option value against the stock price

$0$20$40$60$80$100$120$140Stock priceOption valueStock price = strike
CallPutCall payoff at expiryPut payoff at expiry
Call and put side by side 行数:6
测量CallPut
Price8.265.791
Delta0.5909−0.4091
Gamma0.0220.022
Theta per day−0.0258−0.0124
Vega per 1% volatility0.27470.2747
Rho per 1% rate0.2541−0.2335
计算方法 S
  1. d₁

    d1=ln⁡(100/100)+(0.05+0.252/2)×0.50.250.5=0.229810d_1 = \frac{\ln(100/100) + (0.05 + 0.25^2/2)\times 0.5}{0.25\sqrt{0.5}} = 0.229810
  2. d₂

    d2=d1−σT=0.229810−0.176777=0.053033d_2 = d_1 - \sigma\sqrt{T} = 0.229810 - 0.176777 = 0.053033
  3. Normal probabilities

    N(d1)=0.590880,N(d2)=0.521147N(d_1) = 0.590880,\quad N(d_2) = 0.521147
  4. Call

    C=100 e−0×0.5×0.590880−100 e−0.05×0.5×0.521147=8.26C = 100\,e^{-0 \times 0.5} \times 0.590880 - 100\,e^{-0.05 \times 0.5} \times 0.521147 = 8.26
  5. Put

    P=100 e−0.05×0.5×0.478853−100 e−0×0.5×0.409120=5.79P = 100\,e^{-0.05 \times 0.5} \times 0.478853 - 100\,e^{-0 \times 0.5} \times 0.409120 = 5.79
  6. Put-call parity check

    C−P=Se−qT−Ke−rT=2.469009C - P = S e^{-qT} - K e^{-rT} = 2.469009

    Theta is per calendar day (annual theta ÷ 365); vega and rho are per one percentage point. European exercise; the model assumes constant volatility and rates.

关于Black-Scholes calculator (option price and Greeks)

The Black-Scholes-Merton model prices a European option from the stock price S, the strike K, the time to expiry T in years, the volatility σ, the risk-free rate r and a continuous dividend yield q. A call is worth S·e^(−qT)·N(d₁) − K·e^(−rT)·N(d₂), where N is the standard normal distribution, and the put follows from the same terms. The Greeks measure sensitivity: delta to the stock price, gamma to delta itself, theta to the passing of time, vega to volatility and rho to the interest rate.

With the defaults, a stock at 100, a strike of 100, six months to expiry, 25% volatility and a 5% rate, the call is worth 8.26 and the put 5.79. The call's delta of 0.5909 means it gains about 0.59 for each 1 rise in the stock, and its theta shows it losing about 0.026 a day.

The model assumes constant volatility and rates, log-normal prices and exercise only at expiry. US stock and ETF options are American-style and can be exercised early; index options such as SPX are European and cash-settled.

计算示例

Hull example 15.6

Stock price
42
Strike price
40
Time to expiry
0.5 years
Volatility (per year)
20%
Risk-free rate (continuously compounded)
10%
Dividend yield (continuous)
0%
Call price
4.76
Put price
0.81
d₁
0.769263
d₂
0.627841

核验来源:Hull, Options, Futures, and Other Derivatives, Example 15.6: c = 4.76, p = 0.81, d1 = 0.7693, d2 = 0.6278; Python decimal (prec 50, erf series) gives 4.7594224, 0.8085994

Hull chapter 19 Greeks

Stock price
49
Strike price
50
Time to expiry
0.3846 years
Volatility (per year)
20%
Risk-free rate (continuously compounded)
5%
Dividend yield (continuous)
0%
Call price
2.40
Call delta
0.5216
Gamma
0.06555
Call theta (per day)
-0.0118
Vega (per 1% volatility)
0.1211
Call rho (per 1% rate)
0.08907

核验来源:Hull ch. 19 (S=49, K=50, 20 weeks): price 2.40, delta 0.522, gamma 0.066, theta −4.31/yr = −0.0118/day, vega 12.1 (0.121 per 1%), rho 8.91 (0.0891 per 1%); Python decimal values to 6 dp

Index option with dividend yield

Stock price
930
Strike price
900
Time to expiry
2/12 years
Volatility (per year)
20%
Risk-free rate (continuously compounded)
8%
Dividend yield (continuous)
3%
Call price
51.83
Put price
14.55
d₁
0.544479

核验来源:Hull Example 17.1: c = 51.83, d1 = 0.5444; Python decimal (prec 50) Merton formula gives 51.8329568

At the money with zero rate

Stock price
100
Strike price
100
Time to expiry
1 year
Volatility (per year)
20%
Risk-free rate (continuously compounded)
0%
Dividend yield (continuous)
0%
Call price
7.97
Put price
7.97
Call delta
0.5398
Put delta
-0.4602

核验来源:With r = q = 0 and S = K, d1 = σ√T/2 = 0.1 and C = P = S(2N(0.1) − 1) = 7.9655675 (Python decimal and math.erf agree)

常见问题

What is the Black-Scholes formula?

C = S·e^(−qT)·N(d₁) − K·e^(−rT)·N(d₂), with d₁ = (ln(S/K) + (r − q + σ²/2)T) ÷ (σ√T) and d₂ = d₁ − σ√T. For the defaults, d₁ = 0.2298 and d₂ = 0.0530. Fischer Black and Myron Scholes published it in the Journal of Political Economy in 1973 (vol. 81, no. 3, pp. 637–654); Robert Merton and Scholes received the 1997 economics prize for the work, Black having died in 1995.

What does option delta mean?

Delta is how much the option price changes for a 1 change in the stock price. The default call has a delta of 0.5909 and the put −0.4091; without dividends they always differ by exactly 1. One US equity option contract usually covers 100 shares, so a call with a delta of 0.59 moves roughly like 59 shares of the stock.

What is put-call parity?

For European options with the same strike and expiry, call − put = S·e^(−qT) − K·e^(−rT). With the defaults, 8.26 − 5.79 = 2.469, which equals 100 − 100·e^(−0.05 × 0.5). If market prices break this relation, a riskless profit exists before trading costs, so the put price follows directly from the call price.

How does volatility affect an option's price?

Higher volatility raises both call and put prices, because it widens the range of prices the stock can reach before expiry. The default call's vega is 0.2747, so each extra 1% of volatility adds about 0.27; raising volatility from 25% to 35% lifts the call from 8.26 to 11.01 and the put from 5.79 to 8.54.

Can Black-Scholes price American options?

Only some. US stock and ETF options are American-style, so they can be exercised before expiry. For a call on a stock that pays no dividends, early exercise is never worth it, so the Black-Scholes price is also the American price (Hull, Options, Futures, and Other Derivatives). American puts, and calls just before a dividend, are worth more than the model shows and need a binomial tree or similar method.

“Black-Scholes calculator (option price and Greeks)”有多准确?

准确性取决于输入值和方法的假设。十进制运算使用50位有效数字,但估算、数值方法和源数据的精度可能较低;显示时的舍入并不能消除这些限制。 已按独立来源核验的计算示例:4。 例如,“Hull example 15.6”根据Hull, Options, Futures, and Other Derivatives, Example 15.6: c = 4.76, p = 0.81, d1 = 0.7693, d2 = 0.6278; Python decimal (prec 50, erf series) gives 4.7594224, 0.8085994进行核验。

这种方法出自哪里?

Hull — Options, Futures, and Other Derivatives, ch. 15 (Black-Scholes-Merton), 17 (dividend yield) and 19 (Greeks); Black & Scholes (1973), The Pricing of Options and Corporate Liabilities, Journal of Political Economy 81(3).

关于此计算器

C=Se−qTN(d1)−Ke−rTN(d2),P=Ke−rTN(−d2)−Se−qTN(−d1),d1,2=ln⁡(S/K)+(r−q±σ2/2)TσTC = S e^{-qT} N(d_1) - K e^{-rT} N(d_2),\quad P = K e^{-rT} N(-d_2) - S e^{-qT} N(-d_1),\quad d_{1,2} = \frac{\ln(S/K) + (r - q \pm \sigma^2/2)T}{\sigma\sqrt{T}}

来源

  1. Hull — Options, Futures, and Other Derivatives, ch. 15 (Black-Scholes-Merton), 17 (dividend yield) and 19 (Greeks)
  2. Black & Scholes (1973), The Pricing of Options and Corporate Liabilities, Journal of Political Economy 81(3)

仅用于规划。贷款机构、税务机关和市场采用各自的舍入方式、费用和规则;作出承诺前,请向相关机构确认数值。

已对照来源验证

此计算器包含 4 个已解示例,答案来自独立来源。这些示例会在测试套件中运行,你也可以在此运行验证。

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