My option pricing spreadsheet will allow you to price European call and put options using the Black and Scholes model.
Understanding the behavior of option prices in relation to other variables such as underlying price, volatility, time to expiration etc is best done by simulation. When I was first learning about options I began building a spreadsheet to help me understand the payoff profiles of calls and puts and also what the profiles look like of different combinations. I've uploaded my workbook here and you're welcome to it.
On the "basic" worksheet tab you will find a simple option calculator that generates fair values and option Greeks for a single call and put according to the underlying inputs you select. The white areas are for your user input while the shaded green areas are the model outputs.
Underneath the main pricing outputs is a section for calculating the implied volatility for the same call and put option. Here, you enter the market prices for the options, either last paid or bid/ask into the white Market Price cell and the spreadsheet will calculate the volatility that the model would have used to generate a theoretical price that is in-line with the market price i.e. the "implied" volatility.
The PayoffGraphs tab gives you the profit and loss profile of basic option legs; buy call, sell call, buy put and sell put. You can change the underlying inputs to see how your changes effect the profit profile of each option.
The Strategies tab allows you to create option/stock combinations of up to 10 components. Again, use the while areas for your user input while the shaded areas are for the model outputs.
Use this Excel formula for generating theoretical prices for either call or put as well as the option Greeks:
A Sample formula would look like
=OTW_BlackScholes(c, p, 25, 26, 0.25, 0.05, 0.21, 0.015).
Same inputs as above except:
=OTW_IV(p, 100, 100, 0.74, 0.05, 8.2, 0.01)
If you're after an online version of an option calculator then you should visit Option-Price.com
Just to note that much of what I have learnt that made this spreadsheet possible was taken from the highly acclaimed book on financial modeling by Simon Benninga - Financial Modeling - 3rd Edition
If you're an Excel junkie, you'll love this book. There are loads of real world problems that Simon solves using Excel. The book also comes with a disk that contains all the exercises Simon illustrates. You can find a copy of Financial Modeling at Amazon of course.