Updated: Jan 8, 2019
Calculating implied volatility (IV) is more of a backwards-type calculation.
Since IV is “implied” through each option price itself, you’ll first need to know the price of the option you’re considering and then run that price through an option calculator. You can use this one from the CBOE.
At the bottom-right corner of that calculator, you’ll see the box that will help you solve for IV.
Before that though, you’ll first have to fill in the input section on the left for whatever stock, strike price & expiration you want.
Once it gives you the output results on the right, take the value for the call or put option and put it in the IV box at the bottom-right. It will then give you the IV based on your inputs.