Abstract Estimation is a method used to predict financial requirements by analyzing, calculating, and engineering based on field conditions and bidding documents. To enhance efficiency, there is a pressing need for a simple, swift, accurate cost estimation model. Therefore, this study aimed to establish cost estimation model at the initial planning phase of construction work and to assess its accuracy in estimating cost for road improvement using cost significant model (CSM) compared to actual expenses. The fundamental objective was to facilitate the execution of construction work, ensuring the successful completion. Data collection occurred at the (PUPR) in Aceh Jaya Regency, consisting of 25 contracts for road improvement work spanning from 2018 to 2022. The data included the execution year, road area, total variable cost (y), and the categorization of work item as independent variables (xn). Subsequently, the work data was transformed into data per square meter (m2) for each work item by dividing each independent variable by the area of road improvement work. This showed the cost/m2 for each work item (xn) and the total cost (y)/m2. Annual inflation data was obtained from (BPS) of Aceh province used for calculation projection year. The identification of cost-significant item variables occurred after organizing the data according to work item, adjusting the work cost for the execution year and the work-year cost while considering inflation factor. Additionally, it was observed that 3 most expensive work items represented 80% work item had a substantial impact on the total cost. Classic assumption tests were conducted to confirm the suitability of data for further analysis. The analysis was conducted using multiple linear regression, resulting in a model with y = 69850.515 + 0.879(x4) + 1.085(x5) + 1.221(x7). When cost significant model estimates were compared to the actual total cost of road improvement in Aceh Jaya, the accuracy ranged from +17.46% to -19.30%, which was consistent with Class 3 classification of (AACE) International standards.This classification was suitable for semi-detailed cost estimation in the conceptual phase.