This study develops a web-based decision support system to assist users in planning home construction within budget. The system supports two user groups: contractors and general users/members. Core functions include managing house plans and material lists, searching designs, and real-time budget calculation when alternative materials are selected. The Multi-Criteria Decision Making (MCDM) technique, specifically TOPSIS, is applied to analyze structured and quantitative data such as house plans and material lists, prioritizing and recommending suitable alternatives based on criteria including structure, size, price, material type, and properties. The evaluation with 5 contractors and 25 general users/members confirmed high satisfaction, particularly in planning support, data accuracy, and ease of use. Statistical analysis confirmed significant improvement in budget control and material selection efficiency compared to traditional methods at