Leonora,
That's a simple question that I would have to follow with the phrase...it depends.
Here is something from the eLearning Guild that might provide you with "food for thought".
The rate varies by your education, background/skills, how long you have been in the position, where you live, types of jobs you do, etc.
http://www.learningsolutionsmag.com/articles/1888/One mistake freelancers make is to assume if they take their annual survey and divide it out, they will find their hourly rate. Mathematically, that would be correct but that approach has some flaws.
For example, when you are working in a corporate learning department, your health coverage is covered, you get paid holidays/sick days, your equipment is provided (hardware/software), you don't have to pay for a business license, pay estimated quarterly taxes... the list goes on and on.
I would say, charge a rate that covers your expenses and leaves room for profit, adjust for your skill level, education and compare it to others in your geographical area.
Here's a discussion on just that question. If after reading it you have any questions, please don't hesitate to ask.
https://community.articulate.com/discussions/building-better-courses/what-s-the-going-rate-for-freelance-workHave a great day!