The design of concrete columns reinforced with fibre-reinforced polymer (FRP) bars is currently debatable. The present study proposes a reliability-based approach with the objective of calibrating the optimal strength reduction factor for the design of short rectangular FRP-RC columns under eccentric axial loading according to the ACI-440 guide. The reliability approach relies on a fast hybrid first-order reliability method (FORM)-based response-surface (RS) method. The results of such a hybrid approach have been validated using a Monte Carlo importance sampling (MC-IS) technique. The uncertainty of geometrical, material and loading variables is considered through various dedicated statistical distribution laws. Several design parameters have been considered: load eccentricity, aspect ratio of the concrete section, reinforcement ratio, live to dead load ratio, strength of concrete, and grade of FRP bars. In addition, Top-Bottom and Uniform reinforcement configurations, which are preferred for high- and small-load eccentricities, respectively, are considered. To ensure the generalization of the approach, full combinations between the design parameters are performed, resulting in more than 10 5 structural classes. Thus, calibrated strength reduction factors can cover a wide range of design situations. After demonstrating the possible inappropriateness of ACI-440 rules, the study proposes a novel approach to choose the strength reduction factors based on a quadratic function of the live-to-dead load ratio and load eccentricity. Eventually, the study presents recommendations for the selection of reduction factors distinguishing small and high load eccentricity and concludes with a working example. • A probabilistic calibration of the strength reduction factor given by ACI 440.1R-15 rules is implemented. • More than 100 000 structural classes and two reinforcement configurations are studied to provide a general safety factor. • Live to dead load and load eccentricity to section height ratios significantly affect the strength reduction safety factor. • Recommendation to update strength reduction factor value at 0.6, to be compliant with reliability requirements is made.