This is a very simple freelance writing rate calculator. It will help you to determine a ballpark figure for what you should charge by the hour and by the word. Just remember: this is an estimate of what your rates should be based on a desired annual income. Depending on the project, you may want to charge more or less. Things that will determine your final price will be amount of work, extra requirements of the client, depth of research and any additional factors.
The best way to use these calculations is in a baseline capacity. Determine the smallest yearly income that you can survive on and then calculate the hourly rate needed in order to reach that goal. With that rate in mind, you'll be able to negotiate price confidently without the fear of undercharging.
There may also be situations where charging by the project is more feasible. In these cases, an hourly rate can still come in handy. Simply picture the project and determine each step required including client consultations, interviews, research, writing and editing. Calculate the time it will take to complete each of those steps and then combine them into an overall hourly estimate. Now, it's as easy as multiplying that estimated project length by your hourly rate. The answer will give you a good basis for the per project price.
I'll post some more information about using the freelance writing rates calculator in the next few days. Until then, hope this helps you get what you deserve as a freelancer.