Many new freelancers copy a rate they saw online. The problem is that a freelance rate has to cover much more than an employee's hourly wage.
Start from the take-home pay you want
Decide what you want to earn after tax in a year. Then add your business costs: software, equipment, insurance and accounting.
Count only billable hours
You will not bill 40 hours a week. Admin, sales and learning take real time. If you bill 25 hours a week for 46 weeks, that is 1,150 billable hours a year. At $60,000 take-home, $6,000 of costs and 25% tax, you need about $74.78 an hour.