Glass fibre-reinforced polymers (GFRP) bars have been widely used in reinforced concrete structures as an alternative to conventional steel bars due to their excellent strength and durability properties. Usually, the serviceability limit state controls the design of flexural concrete members reinforced with GFRP bars due to the lower stiffness of GFRP compared to steel. The evolution of the crack width equation through the past decades showed that the concrete cover and the reinforcement spacing are fundamental factors that control the crack width formulation. Experimental observations showed that increasing the concrete cover or the bar spacing increases the crack width at the service stage. However, the literature showed controversial opinions on the effect of other factors on the crack width, such as the concrete compressive strength and the bar diameter. Some researchers ignored the influence of compressive strength and bar diameter on the crack width, and others showed their significant effect on the crack width. The main objective of this study is to present a comprehensive literature review of the available analytical and experimental studies in order to investigate the crack width provisions development and identify the required future work. The design equations proposed by several researchers to predict the crack width at the service limit state were presented and discussed.