Mechanics calculate auto repair estimates by figuring out how long it should take them to do the job and how much the parts should cost, and then adding that together. The time it takes is billed as labor and the parts are billed individually.
The way labor charges are calculated can vary. Some shops charge based on the actual time it takes the technician to complete the repair, while others have a pre-calculated rate depending on the task. The pre-calculated rate is based on "book time," which is the industry standard for how long a particular job should take. Another factor that can affect the labor charge is diagnostic costs. Some mechanics charge for time spent diagnosing the problem, while others do not. All reputable mechanics should be willing to outline their labor charges in detail.
The cost for parts generally includes a mark-up to compensate the mechanic for overhead. This is usually around 30 percent. Many mechanics try to find the least expensive part that is still good quality. They should be willing to tell the customer where they source their parts if asked. They should also tell the customer whether the part is new, rebuilt or salvaged.
Auto repair estimates are usually calculated with the highest possible costs in order to avoid running over budget. Reputable mechanics always contact the customer for approval before doing work that is not included in the estimate.