Software projects typically require effort estimation from the Software Development Life Cycle (SDLC) staff at the commencement of the software development activities. Inaccuracies in effort estimation of software projects early on in the SDLC continues to be a perennial problem. Typically, improved estimates for software projects are provided under circumstances where Requirements Engineering (RE) is completed. RE provides a key reference in the form of requirements for the estimation process. However, RE by itself may consume significant effort demanding the RE phase to be estimated as the first step in the SDLC. It is difficult to establish RE estimates, as RE usually has no tangible reference on which estimates can be based. This paper provides a practical estimation method for large and complex RE processes. We demonstrate using a case study snapshot in a large software organization that the method provides improved effort estimates for the RE process.