A budget is a quantitative expression of a plan for a defined period of time. It may include planned sales volumes and revenues, resource quantities, costs and expenses, assets, liabilities and cash flows. It expresses strategic plans of business units, organizations, activities or events in measurable terms.

A budget (derived from old French word bougette, purse) is a quantified financial plan for a forthcoming accounting period. A budget is an important concept in microeconomics, which uses a budget line to illustrate the trade-offs between two or more goods. In other terms, a budget is an organizational plan stated in monetary terms.

The budget is not just a collection of numbers, but an expression of our values and aspirations. — Jacob Lew

Budget helps to aid the planning of actual operations by forcing managers to consider how the conditions might change and what steps should be taken now and by encouraging managers to consider problems before they arise. It also helps co-ordinate the activities of the organization by compelling managers to examine relationships between their own operation and those of other departments.

The budget of a company is often compiled annually, but may not be a finished budget, usually requiring considerable effort, is a plan for the short-term future, typically allows hundreds or even thousands of people in various departments (operations, human resources, IT, etc.) to list their expected revenues and expenses in the final budget.