Black-Scholes on HP 17BII, 19BII


I would appreciate anyone interested in option pricing on the 17BII and 19BII to try this modification of HP's program. It's a little more accurate, and is a bit smaller.

Modified Black-Scholes:

HP's original version:

Bob Wang


Excellent work Bob! In DataFile V22N3 pp13-21 I did a B-S article about the 12C but included this version for the 17bii which uses a simplified form of the approximation you use:

=========snippet from DataFile =================
This equation is 15% shorter than the one on the HP page and
produces answers 20 times more accurate:


There is another version for the 17bii as well that enables resolving for the any of the 5 inputs, including the implied volatility. This one above could even be shortened again but accuracy suffers a little.

For DataFile, see


ive always been peeved that neither the 17bii nor 19bii have UTPN (normal distribution). it would make this a lot easier.


Thanks for the HPCC link. I'll have to get the CD with your articles. I do like the compactness of your approximation, I have to say that I'm impressed that Black-Scholes can fit on a 12C.



I tried your version for the upper tail and got very inaccurate results. Would you mind checking the routines N(d1) and N(d2)?


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