Including contingency costs helps account for unexpected expenses that arise during a job, such as material price increases, delays, or design changes. Typically, a contingency is a set percentage of the total estimated cost—often ranging from 5% to 15%, depending on the project’s complexity and risk level. Adding contingency costs to your job cost estimate ensures that you have a financial buffer to handle unforeseen issues without affecting your profit margin or requiring renegotiation with clients. This practice improves both job planning and client trust.