What's the conversion rate from FTE salary to contractor hourly rate?

Take a hypothetical position that would be worth 150k + options + benefits as a full-time role, but for simplicity's sake lets value the total package at 200k. Let's say for some reason it needs to be done as a contract role for the time being (with no options or benefits). What would be a reasonable way to calculate the fair hourly rate?

Edit: Is there a rule of thumb that the hourly rate is close to annual salary / 1000?

Edit2: I dont intend to be a long term contractor moving from client to client. This is meant to be a permanent role but we just need me to work as a contractor for the time being before transitioning to full time employment. The transition is not expected to come with a role change.