Doubling Time
Formula : $$Doubling Time = {duration * \log(2) \over \log(FinalConcentration) - log(InitalConcentration)}.$$
Where "log" is the logarithm to base 10 or 2 or any other base.
Units : You can use any time unit for duration. Doubling time unit will be the same.
Cite this website as following:
Roth V. 2006 Doubling Time Computing, Available from: http://www.doubling-time.com/compute.php