What U.S. agency controls the biggest percentage of the discretionary budget?

The U.S. agency that controls the largest percentage of the discretionary budget is the Department of Defense (DoD).

In fiscal year 2023, discretionary spending totaled approximately $1.7 trillion, according to data from the Congressional Budget Office (CBO) and other federal sources. Of this, defense spending—overwhelmingly allocated to the DoD—amounted to $806 billion, representing about 47% of the total discretionary budget.

This figure aligns with historical trends, where defense spending consistently accounts for nearly half or more of discretionary outlays. For comparison, non-defense discretionary spending, which funds all other federal agencies combined (e.g., Health and Human Services, Education, Transportation), was slightly higher at $910 billion in FY 2022 but is spread across numerous agencies, none of which individually rival the DoD’s share.

The DoD’s budget covers military operations, personnel, equipment, and research, making it the single largest recipient of discretionary funds. In FY 2025 projections, the DoD’s base budget request is around $849.8 billion, reinforcing its dominance, though exact percentages shift slightly year-to-year based on appropriations and supplemental funding (e.g., for overseas operations). No other agency comes close—Health and Human Services, the next largest by total budget, leans heavily on mandatory spending (e.g., Medicare, Medicaid), leaving its discretionary portion far smaller.

So, the Department of Defense holds the biggest slice of the discretionary pie, typically hovering around 45–50% annually.