Materials and Tools
First of all you need to figure out what parts and materials are required for the plumbing job. You need to take all materials into account, such as pipes, faucets, toilet parts and bathtubs which are required for that particular project. This is to make sure that you have made a correct calculation of the material costs.
Next you need to measure the distance required for the straight pipes which you need to replace with the faulty ones. You need to calculate the length of the pipes required for the project. Also take into account the materials require for plumbing addition.
Price of each item
After noting what items and the size of pipes required, you need to check the cost of each item from a shop. You can make a list of all the items and then add them to get the total material cost. After adding these material cost, you need to add around $10 in the total for any small items which are needed e.g. screws, nuts or washers.
Next you need to determine an estimate time require for the job. You need to determine the number of hours require. Remember to add the time require for going to the store and buying the materials.
You need to determine your hourly rate. In order to determine the correct hourly rate you can always contact plumbing companies and ask for their hourly rates. Choose the hourly rate which you believe is correct and fair for you. Remember to charge lower if you are new in this business. However, if you are in this business for a long time and have experience then you can charge higher for your services.
In the end you need to determine the final estimate of the plumbing project you are given. You need to multiply the number of hours with the hourly rate and add the material costs with the labour costs. Add around eight per cent to the total for any addition costs which can be either in form of time or materials.