Take your expected salary per annum, pre deductions. Divide that by 200. This is your BASE line break even contracting rate per day. Any thing less, and you're going to have issues financially.
@ $50,000 per annum
50,000 / 200 => 250 per day.
On average, you'd realistically want to be charging closer to Base + 40%. Im my example, this would be $350
just to give yourself time off, $$ for equipment, marketing, growth, insurance, accounting, other general business costs.
Contractors are expensive because we're the business. We take on the risk. We do the HR, taxes, insurance, office rentals, equipment costs/hire. Everything.