Implied Volatility Calculator

Solve the Black-Scholes implied volatility from a quoted option price. Enter the option mid price, option type (call or put), spot, strike, time to expiration, risk-free rate, and dividend yield, and the calculator inverts the pricing formula via bisection to recover the IV that would make Black-Scholes reproduce the quote.

Convergence requires the quoted price to sit between the arbitrage bounds: max(0, S·e^-qT − K·e^-rT) ≤ call ≤ S·e^-qT, with mirror bounds for puts. Bid-ask spreads and illiquid wings are the most common source of non-convergence failures — prefer mid prices on liquid strikes. The same solver runs continuously on the live platform to calibrate the full volatility surface and each ticker's IV/HV history.