The third step in estimating a software project is to compute the schedule estimate. A rule of thumb is that you can compute the schedule from the effort estimate by using Equation 8-1.
Equation 8-1. Software Schedule Equation
If you've estimated that it will take 65 man-months to build the project, Equation 8-1 says that the optimal schedule is 12 months (3.0 * 65⅓). That in turn implies an optimal team size of 65 man-months divided by the 12-month schedules—5 or 6 team members.
Unlike on many other topics in software project estimation, people have published remarkably similar findings on this topic (Boehm 1981). Opinions vary ...