Sure, $4 trillion sounds like a lot.
But it goes fast when your budget stretches from aging highways to medical care to defense and more.
Here are some highlights, broken down agency-by-agency, of how President Barack Obama would spend Americans' money in the 2016 budget year beginning Oct. 1:
Total spending: $156 billion
The budget proposes consolidating the Agriculture Department's Food Safety and Inspection Service with the Food and Drug Administration's food safety oversight in a new agency under the Health and Human Services Department. If Congress goes along with the proposal, USDA would lose one of its main functions.
The administration is proposing to cut $1.6 billion for farmers' crop insurance to pay for other agriculture programs. The program, which subsidizes both the companies that sell crop insurance and farmer premiums, was estimated to cost more than $9 billion last year. There will be little appetite for that reform in Congress, however, where funding for crop insurance has been a priority.
The bulk of the USDA budget is nutrition programs. Food stamps alone are estimated to cost $83.7 billion for the 2016 budget year. Though fewer people are expected to apply for food stamps in the coming years, food prices are expected to keep the cost higher.
Total spending: $12.4 billion
Obama's Commerce Department budget proposes a new Scale-Up Fund, designed to help new startup companies develop technologies that can be manufactured in the U.S.
Obama would expand a network of manufacturing institutes around the country from nine to 45. The institutes are designed to coordinate the federal government's work with local companies and schools to develop technologies that the U.S. can produce.
Spending for the Census Bureau ramps up slightly as the agency prepares for its once-every-decade count of America's population.
Total spending: $585 billion
The proposed budget calls for investment in a broad range of weapons systems, aircraft and ships, along with increased spending on cybersecurity, and other advanced technologies, such as high-energy lasers. The plans include $10.6 billion for 57 Joint Strike Fighters, $11.6 billion for nine new ships; $1.4 billion for submarine development, $1.2 billion for a new long-range bomber and $3.4 billion for 16 P-8 Poseidons, which conduct anti-submarine warfare.
Warning of a maturing long-range missile threat from North Korea and the potential threat from Iran, the Pentagon is asking for $9.6 billion for missile defense.
The administration is proposing a $53.9 billion budget for the intelligence agencies, including war-related funding. As a matter of policy the Director of National Intelligence provides no breakdown of its budget requests, saying that to do so would harm national security.
The budget includes a 1.3 percent raise for service members and department civilians, but seeks changes in health care costs, including requiring retirees who are 65 or older to pay a small annual health care fee.
The war funding would pay for continued counterterrorism operations in Afghanistan and efforts to advise Afghan forces. It also would fund counter-insurgency operations in Iraq, Syria and other hot spots around the globe.
Despite persistent opposition from Congress, the Pentagon is seeking another round of military base closings in 2017 and is asking to retire the A-10 Warthog attack aircraft.
Total spending: $73.8 billion
The budget seeks $1.4 billion to make two years of community college free and as easy to access as high school. To do so, Obama would give grants to states that agree to make tuition free to students who meet certain conditions.Overall, the program is estimated to cost $60 billion over 10 years.
The budget seeks an increase on tobacco tax to make preschool available to all low-and moderate-income 4-year-olds at a cost of $1.3 billion next year, or $75 billion over 10 years. The budget also seeks $750 million for preschool development grants to states to expand access and improve quality of early education programs, meant to lay the groundwork for universal pre-K.
Obama also seeks $1.5 billion in new spending by the Health and Human Services Department for Head Start programs — money that would help make Head Start available for a full day and all year for some children and expand services for expecting parents and very young children.
The budget would provide a $1 billion increase in Title 1 funding, meant to close inequities in education.
ENVIRONMENTAL PROTECTION AGENCY
Total spending: $12.5 billion
Obama's proposal includes $239 million for the EPA to address climate change, including the marquee rules due this summer to cut heat-trapping pollution from new and existing power plants. About $25 million is set aside for states to help them draft plans to meet the power plant rules.
For the first time, the EPA budget establishes a $4 billion fund for use by states that cut pollution blamed for global warming at power plants deeper or faster than required. But that proposal would require Congress to find an offset to pay for it.
Obama's budget also includes $50 million for the EPA to help assist states, tribes and private companies to upgrade drinking water and sewer systems. The budget also calls for $2.3 billion in low-interest loans and grants to communities to make improvements in drinking water and sewage treatment and infrastructure.
HEALTH AND HUMAN SERVICES
Total spending: $1.1 trillion
The president's proposed health care budget asks Congress to authorize Medicare to negotiate what it pays for high-cost prescription drugs. Currently, private insurers bargain on behalf of Medicare beneficiaries. Drug makers have beaten back prior proposals to give Medicare direct pricing power. But the introduction of a $1,000-a-pill hepatitis-C drug last year may have shifted the debate.
Tobacco taxes would nearly double, to extend health insurance for low-income children. The federal cigarette tax would rise from just under $1.01 per pack to about $1.95 per pack in 2016. Taxes on other tobacco products would also would go up to provide financing to pay for the Children's Health Insurance Program through 2019. The federal-state program serves about 8 million children, and funding technically expires Sept. 30.
Starting in 2019, the proposal increases Medicare premiums for high-income beneficiaries and adds charges for new enrollees. The charges for new enrollees include a home health copayment, changes to the Part B deductible, and a premium surcharge for seniors who've also purchased a kind of supplemental insurance whose generous benefits are seen as encouraging overuse of Medicare services.
The plan would end the budget sequester's 2 percent cut in Medicare payments to service providers. The budget also calls for Medicare cuts to hospitals, insurers, drug companies and other service providers.
Total spending: $48 billion
Obama seeks to spend up to $162 million more next year to help handle potential increases in the number of unaccompanied children caught crossing the border from Mexico illegally. Customs and Border Protection would get up to $134.5 million more, depending on how many children are caught crossing illegally. Immigration and Customs Enforcement, which transports children caught crossing the border illegally, would get up to a $27.6 million increase.
The proposed CBP budget also includes $373 million to buy and maintain technology and tactical infrastructure along the Southwest border.
New spending for security improvements at the White House complex has also been added to the budget after a series of presidential security breaches in the last few months.
HOUSING AND URBAN DEVELOPMENT
Total spending: $48.35 billion
A new program designed to help communities hit by hurricanes, flooding or other natural disasters to become more resilient to future disasters will require $500 million.
The budget also seeks to more than double spending to $248 million for "choice neighborhood grants," which communities can use to improve housing stock, transportation and other services for distressed neighborhoods with high rates of poverty. It also seeks about $2.5 billion for a wide range of programs dedicated to helping the homeless.
A reduction in mortgage insurance premiums that would enable 250,000 new homebuyers over a three-year period is also proposed in the budget.
Total spending: $15 billion
The budget includes $859 million in new spending to mark the centennial of the National Park Service in 2016 by upgrading services and facilities at national parks throughout the country. It also proposes $150 million for "challenge grants" to leverage private donations to parks.
The budget again floats new fees and other regulatory reforms to increase revenue from oil and gas production on federal lands and waters, and calls for changing a fee system designed to clean up abandoned coal mines. The budget would extend tax credits for wind and solar projects.
The budget also seeks about $1 billion to operate and upgrade federally run schools for 48,000 Native American children on reservations, including tens of millions in new funding to repair dilapidated schools.
Total spending: $31.8 billion
The budget proposes $30 million to support a competitive program to fund the purchase of body cameras, expanded training and oversight for police officers.
The proposal also includes roughly $15 million for programs and research aimed at countering violent extremism.
The budget calls for roughly $480 million to the Executive Office of Immigration Review to address a problematic backlog of immigration cases. It would provide funds supporting the hiring of an additional 55 immigration judge teams and to expand legal representation for unaccompanied children.
It would invest $146 million to improve re-entry and recidivism programs in the Bureau of Prisons, including increasing mental health staff and providing cognitive behavioral treatment.
It would expand pre-trial diversion programs for non-violent offenders in keeping with Holder's "Smart on Crime" initiative. It also calls for research to study the effectiveness of the program, which called on prosecutors to rein in their use of mandatory minimum sentences for non-violent drug offenders.
Total spending: $79.8 billion
The budget proposes a $2 billion initiative to assist as many as five states that wish to launch paid-leave programs for workers. It is seeks $207 million to make saving easier for millions of Americans currently without employer-based retirement plans.
The Occupational Safety and Health Administration would receive $592 million to foster compliance with safety and health regulations, inspect hazardous workplaces and strengthen protection of whistleblowers. Another $395 million would go to the Mine Safety and Health Administration to help protect workers in one of the nation's most dangerous industries.
Total spending: $63.3 billion
The budget asks Congress to set aside $117 million to counter "aggressive acts" by Russia in Ukraine and would allocated $51 million to blunt Russian pressure on Moldova and Georgia. It would provide Ukraine with $154.1 million in direct economic aid.
It would dedicate $3.5 billion to counter the Islamic State in Iraq and Syria, respond to deteriorating conditions in Syria, and assist with humanitarian needs among refugee populations in the region.
It allocates $1 billion for programs that will try to reduce illegal migration from Central America, particularly of children.
The budget seeks $1.5 billion for the fragile Afghan government and another $963 million to fund American operations in the country, including $124 million for security upgrades at the embassy in Kabul. Next door in Pakistan, the budget asks for $917 million worth of programs.
Total spending: $94.5 billion
The six-year highway and transit plan would get a one-time $238 billion infusion from the general treasury. Some of the money would be offset by taxing the profits of U.S. companies that haven't been paying taxes on income made overseas. That infusion comes on top of the $35 billion a year that normally comes from gasoline and diesel taxes and other transportation fees.
The proposal would triple spending, from $11 billion to $31 billion, for the National Highway Traffic Safety Administration's office that investigates whether cars and trucks should be recalled, and double the office's personnel.
Total spending: $577.1 billion, including interest paid on the national debt.
The biggest portion of the Treasury Department's discretionary spending goes to the IRS, which is seeking an 18.3 percent increase to $12.9 billion for 2016.
Total spending: $165.4 billion
The budget includes $60 billion to improve veterans' medical care, a 7.4 percent increase over current spending. Of that, $7 billion will be used to expand improve mental health services, $1.4 billion for programs to reduce homelessness among veterans and $622 million would go for medical research, including advances in prosthetic limbs to help those wounded in war.
Another $85 million is proposed to hire new staff to reduce a backlog of disability compensations claims paid by the Veterans Benefits Administration.