Off-site construction offers improved quality control, faster project completion, and reduced on-site disruptions compared to traditional on-site construction methods. Steel fabrication plays a pivotal role in off-site construction, as it enables the precise manufacturing of structural components in a controlled environment, ensuring enhanced accuracy and efficiency during assembly at the construction site. In steel fabrication plants, low productivity estimates lead to cost overruns, project delays, resource allocation problems, and reputational damage. To mitigate these consequences, this study aims to develop an accurate estimation model to predict production time in a steel fabrication plant. This study involves three main parts: (1) time studies in steel fabrication plant stations and fitting linear regression (LR) models to estimate productivity; (2) extraction of project complexity from 3D models using application programming interfaces (API); and (3) estimating projects productivity using the LR model and extracted features. This research focuses on six stations on a production line. Using industrial project productivity reports, the results of this study show an average correlation of 95% with actual duration at each station. Cost control, timely project completion, and client satisfaction are the significance of precise productivity estimates.