The use of fibre reinforced polymer (FRP) bars as reinforcement for concrete is nowadays a widely spread technique, well supported by the durability of the material, especially in harsh environments. Steel corrosion raises indeed maintenance costs while reducing the durability of reinforced concrete structures. The innovative and alternative approach to replace steel bars helps to prevent degradation and deterioration of the concrete structure over time but, at the same time, opens questions on the reliability of this kind of non-metallic reinforcement. The last few years have been therefore interested in a rise in the definition and application of design regulations for FRP-reinforced concrete (RC) members. The design of FRP bars is indeed now included in different national and international design guidelines and has been also recently introduced in the revision of EN 1992-1-1 (2023). The value of partial factors for the calculation of design strength there used seems lacking of a sound basis. Starting from a large experimental campaign for the assessment of various FRP bars by different manufacturers, the paper will analyse the database collected by using the design-by-testing approach of EN 1990 to calibrate the partial factors. A comparison will be therefore conducted with prescriptions by national and international provisions, suggesting values which may be taken into account in future revisions of building codes.