Contractors should not overdo their productivity when working for an hourly rate, according to one expert.

Sonia Mansfield, content editor of PsPrint, writes on Freelance Folder that freelancers must be realistic about how much work they can manage when giving a client an estimate.

"If you give clients the expectation that you can get a project done in a few days (regardless of the hours) they may still be under that impression when you do the same amount of hours, but on 'real person' time–meaning, eight to nine-hour days," she said.

Other tips include researching similar contractors to find out their rates, which should make sure the work is neither under or overvalued.

She advises contractors to have in mind the least they are willing to be paid per hour, which means they should not end up doing work for too little money.

In addition, it is important for a freelancer to estimate their non-billable contributions, which can be reduced by using a tracking system, although never eliminated entirely.