It is often assumed that the Peierls stress of single dislocations can reflect accurately the macroscopic yield stress. Here, dislocation dynamics simulations show that the yield stress‐to‐Peierls stress (Y/P) ratio remains within a small range of ≈0.3 ± 0.1, over a wide range of initial dislocation density, mobile dislocation fraction, and temperature which affects cross slip. This range of Y/P arises from the typical stress concentration ahead of dislocation pile‐ups. The results explain why Y/P was observed to be around one‐third in previous experiments.