What formula to use to calculate # of project team for executing project activities?

Estimate Activity Resources has now moved from the Time Management chapter in PMBOK 5 to the Resource Management chapter in PMBOK 6. I get confused between the two sometimes. Anyway it's on page 320.

Sante, thanks for your page reference but I could not find much details for the formula of FTE.

How about this Riyadh:

https://www.wikihow.com/Calculate-FTE

I've been having similar conversations, lately. How do you estimate something you have not done before? How do you know how long doing something new will take? How do you know how many people it will take to do it?

The short answer is that you don't know. Estimating tools, like those listed in the PMBOK Guide, help you develop a more accurate estimate, but it will take time to refine the final answer.

Some important factors are:
* Understanding the work to be done
* Determining whether tasks can be performed by one or multiple people - does adding more people speed it up?
* Knowing the skill level, velocity, and availability of the workers. John may be twice as fast as Jim, but Jim is more thorough and John is not available.
* What level of quality do you require? John may be faster, but sometimes his work quality is poor and needs to be redone, which can take longer.

The more familiar you are with the work that needs to be done and the people doing the work, the more accurate your estimates can be.