How do i write a salary range?

Research

Research what an average professional in the field earns. This can be done by checking professional journals or tools associated with job sites such as Career Builder, Monster and others.

Compare

Compare your experience to that of the average professional. If you have unique skills or special experience, take this into account when preparing your salary range. Likewise, if you have no experience, consider asking for the low end of the range or even slightly less.

Write a range in which the bottom number is equivalent to the lowest that you would reasonably entertain. However, if you have unique skills, write a range that is at the high end of what you researched.

Source:

Career Builder: Salary calculator

Monster: Salary Range