How much of the US federal budget was defense spending in 2020 vs 2024?

1. Why numbers diverge: competing definitions and budget baselines create different stories

Sources disagree because they measure different slices of government spending and use varying baselines for the “federal budget.” Some reports count only discretionary defense outlays (the Department of Defense appropriation), while others include broader national security-related items or use total federal outlays as the denominator. For 2020, the Department of Defense and oversight reports cite defense totals around $714 billion to $721 billion, but the Congressional Budget Office’s overview of fiscal 2020 frames federal outlays and deficits in a broader context that changes percentage calculations ^{[1] [5]}. For 2024, one congressional funding summary lists the defense appropriation near $824.3 billion, while other public-facing aggregations cite figures closer to $841–$872 billion, and analysts note the difference stems from whether supplemental war funding, defense-related mandatory spending, and other accounts are counted as defense ^{[2] [3] [4]}. These definitional choices produce the range of 11%–15% reported by different outlets.

2. The 2020 baseline: official estimates and alternative tallies

Official reports and watchdog reviews give 2020 defense spending roughly $714–$721 billion, but the percent-of-budget result varies. The Department of Defense and GAO-type presentations focus on the appropriation amount, which, when compared to a broader federal outlay figure, produces different percentages than when compared only to discretionary spending. One congressional infographic on fiscal 2020 outlines the federal budget’s components—mandatory spending, discretionary spending, and interest—and shows that defense is a large share of discretionary outlays but a smaller share of total federal spending, which includes Social Security, Medicare, and other mandatory programs ^{[6] [1] [5]}. As a result, an 11% figure for 2020 appears in multiple public summaries that compare defense to total federal outlays, while other comparisons that isolate discretionary spending will show a higher share.

3. The 2024 picture: larger dollar totals but mixed shares

By 2024 reported defense appropriations rose to the mid-$800 billions—numbers commonly reported include $824.3 billion (congressional funding summary) and public aggregates in the $841–$872 billion range ^{[2] [4]}. Public aggregators and think‑tank tallies translate those sums into shares of the federal budget and commonly report about 13%–13.3% for 2023–2024, reflecting defense’s continued dominance among discretionary programs but its smaller share relative to mandatory spending and interest on the debt ^[3]. Some longer‑term forecasts note defense as a stable but slightly declining share of GDP over the coming decade despite nominal increases in dollars, which helps explain why increased nominal defense spending does not automatically translate into a much larger share of total federal spending ^{[7] [3]}.

4. Which approach answers the original question most directly?

To answer “How much of the US federal budget was defense spending in 2020 vs 2024?” one must first choose the denominator: total federal outlays or total discretionary spending. If using total federal outlays, multiple public compendia show about 11% in 2020 and roughly 13% in 2023–2024, reflecting both nominal increases in defense appropriations and inflation‑adjusted changes in other federal commitments ^[3]. If instead one isolates discretionary spending, defense typically consumes a substantially larger share (often a plurality of discretionary dollars), so those percentages will be higher. Analysts and policymakers sometimes emphasize the discretionary comparison to make the scale of defense within annual appropriations more visible ^{[5] [2]}.

5. What to watch and what’s left unsaid: agenda cues and methodological gaps

Different outlets emphasize figures that best support their narrative: watchdog reports and defense budget advocates highlight nominal increases and programmatic needs, while fiscal watchdogs stress percentage shares versus total outlays or GDP to frame priorities ^{[1] [3]}. Several summaries referenced here omit clarifying whether supplemental war funding and defense-related mandatory programs are included, and they sometimes use different fiscal‑year definitions; these omissions materially affect the resulting percentages. For a precise apples‑to‑apples comparison, use a single source’s definition for both 2020 and 2024—preferably the Office of Management and Budget or the Congressional Budget Office—and compare the same line items and denominators across years ^{[5] [2]}.