Billables in law refer to the hours worked by an employee for an employer that are billed to the employers client. In certain professions, particularly in law firms, employees are required to bill a certain number of hours to clients each year. Billable hours are the most used by most private lawyers and law firms to calculate the value of their work, with clients being assessed "a set rate, plus expenses, for each hour that the lawyer — or those working with the lawyer — devote to the case".

There are tasks that a lawyer does that are just part of the work needed to work at a law firm, and then there are tasks that are directly related to the client’s case. Dedicated time spent on tasks directly related to a client’s case can be billed for the most part to the client. These are the hours (and the type of time) that law firms want to maximize so that they can run a profitable business.

Lawyers can track billable hours with a billable hours chart, which is a standardized template that helps users track, calculate, and invoice clients based on increments of an hour spent working billable hours. A billable hours chart is a simple table to help lawyers quickly calculate how many increments of an hour to charge, based on how long they worked. Most lawyers adhere to 1/10th of an hour (aka six-minute) increments.

Billable hours are important for one simple reason: it’s the primary way law firms generate income. This is generally why almost every law firm mandates billable hour requirements or has a billable hour target for each of its attorneys. Depending on a firm’s billable hour requirement, an attorney’s compensation, work/life balance, and career opportunities will vary.