Freelance rate floor: price for billable hours, not calendar hours
A sustainable freelance rate has to cover unpaid admin time, selling time, taxes, expenses, and weeks away from client work.
Your rate is carried by billable capacity. If only half of your work week is billable, those hours must support the whole business.
Separate working hours from billable hours
Sales calls, proposals, bookkeeping, learning, and revisions may be necessary work, but they do not always show up as billable hours on an invoice.
Include the cost of being independent
Software, equipment, insurance, health coverage, unpaid time off, and tax reserves should be included before you treat a calculated rate as sustainable.
Use the result as a floor
The calculated hourly rate is the minimum planning number. Project risk, urgency, value, and client complexity may require a higher quote.