Infrastructure development is an important need to support activities in a region. One of the utilities is in the form of drainage provided to drain rainwater. Along the Tugu barat street, Sampang, Cilacap already has drainage, but every time it rains, there is often a puddle on the road which disrupts the flow of traffic. This study aims to analyze the drainage capacity of Tugu barat street of Sampang using the rational method. The data used is rainfall data. Based on the hydraulic analysis, the results showed that the existing drainage capacity was still able to accommodate rainwater runoff because the existing Q channel (0.634 m3 / sec) was greater than the Q channel plan (0.0035 m3/sec).