Write down on all the details of the design for your project. If you have a blueprint, refer to it carefully. List all the materials you are going to need and their quantities. Then list how much these materials will cost you. Include any transportation costs for getting them on site. Look at what you are planning to build, and price each item individually. Different materials, types of design and quality will all have an impact on the final cost of the project.
Group your costs into different categories. There is much more to consider than just the raw materials. Calculate the costs of any demolition required (including removing debris). Clearing and setting the foundation is another group of costs, and can vary widely depending on the type of foundation you are building on. Another group of expenses is your financing costs. Interest, bank charges and relevant local taxes should all be included. The fees required for inspectors, architects and permits form another group of expenses. Grouping your costs in this way will help further refine your calculations, as well as reveal any areas that you may have overlooked.
Include the costs of any subcontractors that you are planning on using. You should obtain written estimates, be clear about how much variation is permitted within these quotes and clarify whether they include taxes and materials. If not, include these in your calculations.
Complete an estimate for each category of the project. Then add them together to form a final total estimate. Grouping the project in this way will help you track your expenses. If every expense is assigned a category, you will find it easier to control allotted money.
Use an online estimator tool to check your final estimate. It's worth trying a couple of sites, as they may include items you may have accidentally excluded. This will help you to get the most accurate picture possible of your final costs. Get a Quote, Remodeling My Space and Home Design Directory all have notable estimator tools. See the Resources section for contacts. Refine your figures accordingly.