Does any one knows the formula how Thinkorswim is calculating their option Theoretical price? Is there an easier way instead of using Black Scholes. I am asking because I want to create a program to calculate it.
Why do you want to calculate it yourself? What will you do with it? These programs estimate the Ivol from the current midpoint.The problem is that they don't have accurate interest rates (Including hard to borrow rates) and dividend flows.You need a platform that allows you to make adjustments and then you won't have to do it yourself.
I'm scanning 20 stocks in multiples time frames I get my signals however I want to calculate their risk reward so I need the theorical price to wid out small trades
For that you don't have to calculate your own values. You only need the current NBBO and a way of determining where you can get an execution. You will have to make an assumption of how aggressive you will have to be to buy or sell an option vs the NBBO.
> accurate interest rates (Including hard to borrow rates) and dividend flows Exactly. Most or all the "mispricings" his "scanning" discovers will be because of this.
Erick: While not a direct response to your question... I want to insure you are aware that the TOS "Theo price" is a function of their "Implied Volatility" value for that strike, which is dependent on the method YOU select for "Volatility calculation mode:" See setting below: Your Achilles heel will be your derivation of IV, for any formula you attempt. (Not the only issue, but the most problematic one) <- My 1.87 cents. (not quite 2 cents)
The average trader does not need "really" accurate Ivols, because your are not likely entering orders on that are vol orders. eg Buy 100 XYZ July 40 calls at a 42.5 vol vs stock at a XX delta. Most trader use it as a reference to see where options are trading vs other strikes or the past. Having correct inputs will be more useful than the "best " model. You can normally tell when the inputs are wrong when the ATM calls and puts have Ivols that are much different. Mostly, puts appear much higher.
@rmorse Could you elaborate more about using The National Best Bid and Offer (NBBO). I thought that the NBBO was for the brokers to give you a the best (lowest) available ask price and the best (highest) available bid price. So what that has to do with expected future theoretical price? Let said that SPY is at 199 and the call option it is price at .90 cents and my expected move it is 205 in few hours. How I can calculate with the NBBO the price for the same option for intraday? Am I missing something?
If that is what you need it for, no it can't be used that way. Many of my clients use Silexx OEMS. You can add a column for theoretical option price. Then, change the stock price to 205 and make any adjustments to Ivol you want and get a new theo price of the option based on your simulation. You can also move the date if you like. This is what you can adjust. http://www.silexx.com/