If I understand you (and the other replies) correctly, the advice is to ignore the benefit value of PTO when estimating the hourly equivalent rate, then add it back in after the fact based on... something?
Is there a better formula than $TOTAL_COMP / $TIME_WORKED?
Folks get hung up on rule-of-thumb advice like hourly rate * 2.5 because they're thinking about their take-home pay and not the cost of employment. In many defense contracting roles, the "fully burdened rate" for contracts is 2.9-3.5x the employee's pre-tax pay. When switching to contracting you can compete by offering better services and by undercutting your (large company) competition -- and that's just where you start. Once you establish yourself as a better performer you can demand a higher price also.