An original method is highlighted to determine precisely the friction factor of laminar flows in capillaries. The experiments were performed at Reynolds numbers ranging from 10 to 1,000 using a transient method and a steady-state method. The results deduced from all the implemented methods are in good agreement. Nevertheless, uncertainties differ from one method to another. A set of experiments were carried out and specific processing methods were developed. Among these methods, it was found that the integral method is the most accurate one. The friction factor obtained for capillary diameters of 320 and 530 gm are slightly higher (5.5 and 4.2%) compared to the Poiseuille law.