Covered call calculator

Type the stock price, the strike, the days to expiration, an implied volatility for pricing and a historical volatility for the probabilities. The calculator shows the premium, the static return (premium ÷ stock price), the return if called, the effective sale price, how much of a drop the premium covers, and the chances of finishing in the money and of touching the strike, all under a lognormal model. It leaves out dividends, which are a common reason calls get assigned early.

The return if called and the static return answer two different questions: what the trade produces if the shares are taken at the strike, and what it produces if the stock goes nowhere. Both are per share and before fees. The chart draws the covered call next to simply holding the shares, so the upside the call gives away above the strike and the cushion the premium adds below it are side by side.