My estimate math:
R = t × [1.1^ln(n+p) + 1.3^X]
R - time it really takes.
t - shortest possible time it would take without need to communicate.
n - number of people working and involved during the process, both customers and developing organization.
p - longest communication distance network involved in the project (typically from the lowest level developer to the end user)
X - number of new tools, libraries, techniques, used in the process.
Example. Project involving one developing writing code. Project would take 2 weeks (t=2), but it has 5 people (n=5) involved total, only 1 new tool (X=1) and longest communication distance is 4.
2×(1.1^ln(5+4) + 1.3^1) = 4.5 weeks.
replies(3):