From Bob Jensen at Trinity University http://www.trinity.edu/rjensen/

The following table is from a Black-ScholesCalculator.xls Excel spreadsheet file on the path http://www.cs.trinity.edu/~rjensen/Calgary/CD/FAS133OtherExcelFiles/

This partial Black-Scholes Model Calculator was created by Bob Jensen at Trinity University        
 http://www.trinity.edu/rjensen/                    
                     
The page numbers below refer to the second edition of my ACCT 5341 textbook by Robert Strong.      
Derivatives:  An Introduction by Robert A Strong, Edition 2 (Thomson South-Western, 2005, ISBN 0-324-27302-9)    
                     
The purpose of the derivations below is to question the outcomes of online Black-Scholes model calculators.    
                     
                     
0.158900 Time Remaining parameter on Page 140 (in years)            
57.998500 Time Remaining parameter on Page 140 (in days)            
1.906800 Time Remaining parameter on Page 140 (in months)            
35.75% Volatility parameter on Page 143 (as a percentage)            
6.10% Interest Rate parameter on Page 140              
$70.75 Spot Price                  
$70.00 Strike Price                  
                     
-0.2140 d1 on Page 143 (for input into a standardized normal distribution)          
-0.0715 d2 on Page 143 (for input into a standardized normal distribution)          
                     
0.415273529 N(d1) using NORMSDIST() statistical function in Excel            
0.471499912 N(d2) using NORMSDIST() statistical function in Excel            
                     
$3.62 BSOPT Price of an European Put Option on Page 143            
                       
                     
0.2032 d1 on Page 133                  
-0.0229 d1 on Page 134                  
                     
0.5805 N(d1) using NORMDIST() statistical function in Excel            
0.4909 N(d2) using NORMDIST() statistical function in Excel            
                     
$7.04 BSOPT Price of an European Call Option on Page 133            
                     
This should help you derive your own BSOPT calculator.              
All you have to do is derive your own functions for computing the d1 and d2 parameters.        
                     
Now let's consider compare the above answers with several online calculator alternatives.        
                     
                     
$3.62 Put value derived above that is also given on Page 143 of the Strong textbook      
$3.33 Put value from the option price calculator at  http://www.hoadley.net/options/optiongraphs.aspx?     
$3.24 Put value from the option price calculator at  http://www.blobek.com/black-scholes.html      
$3.30 Put value from the option price calculator at  http://www.erieri.com/scripts23/blackscholes/blackscholes.exe/Calculate
                     
                     
$7.04 Call value derived above that is also given on Page 143 of the Strong textbook      
$4.76 Call value from the option price calculator at  http://www.hoadley.net/options/optiongraphs.aspx?     
$4.66 Call value from the option price calculator at  http://www.blobek.com/black-scholes.html      
$4.73 Call value from the option price calculator at  http://www.erieri.com/scripts23/blackscholes/blackscholes.exe/Calculate
                     
If anybody can explain the above discrepancies, I'd sure like to know about it.           
Bob Jensen mailto:rjensen@trinity.edu