Do the arithmetic on $40 trillion and the interest bill it carries

Numbers with twelve zeros have a way of losing all meaning. Say "forty trillion dollars" and the eyes glaze over, the way they do when a flight attendant starts the safety speech. So let us do something rude and old-fashioned. Let us divide.

Division is the great enemy of political abstraction. It takes the number that sounds like the distance to a star and turns it into a number you can compare with a mortgage payment. Here is the arithmetic, from the Treasury's own count, with every step shown.

The two numbers on the page

The Treasury publishes the total public debt outstanding every business day in a data set called Debt to the Penny. Two of its readings frame this post.

• November 4, 2025: $38.05 trillion.
• November 5, 2026: $40.56 trillion.

That is one year and one day apart. The subtraction is easy: $40.56 trillion minus $38.05 trillion is $2.51 trillion. In twelve months, the federal debt grew by two and a half trillion dollars.

A word about what the term means before we go further. "Total public debt outstanding" is the sum of two things: debt held by the public and intragovernmental holdings. Debt held by the public is what Treasury owes to investors outside the federal government: individuals, banks, pension funds, mutual funds, foreign governments and the Federal Reserve. Intragovernmental debt is what one part of the government owes another. The largest example is the trust funds, such as Social Security's, which hold special Treasury securities in exchange for the surplus payroll taxes they once collected. The Treasury's Debt to the Penny page reports both lines and their sum, and the Congressional Budget Office's reports focus mostly on debt held by the public. If you quote one number, say which one. The $40.56 trillion figure is the total.

The daily arithmetic

November 5, 2026 falls 366 days after November 4, 2025: the 365 days from November 4 to November 4, plus one more. So divide:

$2.51 trillion divided by 366 days is about $6.86 billion a day.

That is every day, weekends and holidays included. It is about $286 million an hour, around the clock. Divide by the 86,400 seconds in a day and you get roughly $79,000 a second. A family that took in $79,000 in a year and lived on it would be, by this measure, exactly one second of Washington's borrowing. Each tick of the clock adds a year of an upper-middle-class income to the tab.

I'll admit this is the part where I am tempted to make a joke about the Treasury's idea of a rounding error, but the joke writes itself, so let me just say the number plainly. The debt grew by almost seven billion dollars before lunch on a typical Tuesday.

The household arithmetic

The per-household figure takes one assumption, which I will label as one. The Census Bureau's 2025 estimate counted about 134.8 million households in the United States; for round numbers, this post uses 135 million. Check the Census Bureau's latest figure and adjust the division yourself.

• The one-year increase of $2.51 trillion, divided by 135 million households, is about $18,600 per household.
• The whole debt, $40.56 trillion divided by 135 million, is about $300,000 per household.

A word of caution on these figures, because I do not want to be accused of overselling. The debt is not a bill that will arrive at each house. It is owed by the government, paid out of the taxes of every year's taxpayers, and it will be rolled over, serviced, grown and, one hopes, eventually reduced. The per-household figure is a way of making the scale visible, not a prediction that anyone will write a check. But the figure does carry one real lesson: a debt that is large relative to the households who must ultimately pay for it limits what the government can do for them.

What interest costs: the one-point rule

Now the part that matters more than the debt itself. A debt is a promise to pay interest, and interest does not wait.

Here is the rule of thumb you should carry in your head. On a debt of $40 trillion, each one percentage point of average interest costs $400 billion a year. The arithmetic: 1 percent of $40 trillion is $0.4 trillion. On the actual figure of $40.56 trillion it is about $405.6 billion.

Now look at a table. These are hypothetical average interest rates, applied to a round $40 trillion, to show scale. The real average rate is published by the Treasury in its monthly interest expense data, and I will not guess at it.

Two things follow. First, a change of one point in the average rate moves the annual bill by about $400 billion. That is a very large sum by any measure. Second, the average rate does not move overnight, because the government's debt comes due in pieces. Treasury issues bills that mature within a year, notes that mature in two to ten years and bonds that run for twenty or thirty. As old debt matures, the Treasury refinances it at current rates. A rise in interest rates therefore feeds into the average slowly, over years, and a debt with a short average maturity feels the change faster. That is the quiet danger: the bill for a decision made in a low-rate year arrives, and arrives larger, in a high-rate year.

A refinancing, worked by hand

Make the slow arrival of the bill concrete with a hypothetical. The numbers are invented for the example and are not a forecast.

Suppose $1 trillion of Treasury notes was issued in a low-rate year at an average of 1 percent. Interest on it was $10 billion a year, because 1 percent of $1 trillion is $0.01 trillion. Now the notes mature and the Treasury must borrow $1 trillion again to repay the holders, and the going rate is 4 percent. The new interest bill is $40 billion a year, because 4 percent of $1 trillion is $0.04 trillion. The same trillion dollars, borrowed for the same purpose, now costs $30 billion a year more, and nothing was bought with the difference.

Repeat that across the many trillions of dollars that mature over a few years, and you see why the average rate creeps up even if the Treasury never borrows a cent of new money. This is the mechanism that turns a low-rate era into a high-bill era. It is also why a conservative should be wary of any claim that the debt is cheap to carry. It is cheap to carry only until it has to be rolled over, and the Treasury rolls over a great deal of it every year.

Add the new borrowing on top. If the government adds $2.51 trillion in a year, as it did between the two dates above, and that new money is borrowed at 4 percent, the added debt alone carries about $100 billion a year of interest from then on: 4 percent of $2.51 trillion is about $0.1 trillion. And that is the interest on one year's increase. The next year's increase carries its own. The bill is a staircase, and the government is walking up it.

Debt, interest and what they crowd out

Here is the claim the title of this post carries: interest crowds out everything else. I should explain the mechanism, so that no one thinks I am using a slogan.

The federal budget has a limited number of dollars and a long list of claimants: Social Security, Medicare, Medicaid, defense, veterans, roads, courts, research, and the rest. Interest is different from every other claimant in one way. It is not a choice. Congress cannot vote to skip it. If the government does not pay interest on Treasury securities, it defaults, and the entire system of American credit, on which every other borrower's rate depends, is shaken. So interest is a first claim on revenue, ahead of programs that Congress can adjust.

When interest takes a bigger share, there is less left for the programs voters care about, or else more borrowing is needed to pay for them, which raises the interest bill further. In the Congressional Budget Office's reports, net interest, the interest the government pays on debt held by the public minus the interest it receives, has been rising as a share of the economy, and the CBO has reported that it has become one of the largest items in the budget and is projected to exceed what the government spends on national defense. I would ask you to read the budget tables yourself, because the exact comparison depends on the year and the projection you consult, and the CBO's Budget and Economic Outlook sets out net interest alongside Social Security, Medicare, Medicaid and defense in a single table. Look at the line, compare it with the others, and judge whether interest has become a main course. The Treasury's Monthly Treasury Statement gives the same story with actual figures, month by month.

For a more complete view of how Washington tells the story, and the myths that make the story more comfortable, see Seven myths about the national debt that Washington finds convenient.

The steelman: "the debt is manageable"

Here is the best case for relaxing, as its defenders state it.

One, the debt should be measured against the size of the economy, not in absolute dollars. A $40 trillion debt in an economy that produces many trillions of dollars a year is a ratio, and countries have carried higher ratios for long periods. Two, the United States borrows in its own currency, and the dollar is the world's reserve currency, so there is steady demand for Treasury securities. Three, interest costs depend on rates, and rates can fall. Four, a growing economy makes the ratio shrink even if the debt rises. Five, Japan has carried a debt far larger than ours relative to its economy for years without a collapse.

Each point has something to it. The ratio matters more than the raw number, and the demand for Treasury securities has made borrowing cheap for a long time. I examine the Japanese case in japan's debt is far larger than ours, so why has it not collapsed yet, and the answer is not as comforting as it looks.

The answer, in numbered points

One: the ratio is not a fixed destination. A debt that rises faster than the economy raises the ratio, and a higher ratio does not become sustainable by being described as a ratio. The pace shown above, $2.51 trillion in a year, must be compared with the growth of the economy over the same period. If the economy did not grow by a larger sum in dollars than the debt did, the ratio worsened.

Two: "rates can fall" is a hope, not a plan. The interest bill depends on a variable no one in Washington controls. Borrowing on the assumption of low rates is like taking out an adjustable-rate mortgage on the assumption that the bank will be kind. The arithmetic of the table above shows what happens if it is not.

Three: reserve-currency status is a privilege, not a guarantee. It exists because the world trusts American institutions and American restraint. A country does not keep that trust by testing it.

Four: every dollar of interest is a dollar that does nothing. A dollar spent on a road leaves a road. A dollar spent on a soldier leaves a defended country. A dollar spent on interest leaves a creditor. It is not wasted in the sense of being stolen, but it buys nothing new for the people who pay it, and as the share rises, there is less to spend on the things the government is actually meant to do.

Five: the Founders feared exactly this. Thomas Jefferson wrote that the earth belongs to the living, and argued that one generation should not bind another by a debt it could not repay. Alexander Hamilton, the great champion of public credit, insisted that borrowing be matched by a plan to extinguish the debt, which I describe in Hamilton's 1790 Report on Public Credit and what honest borrowing requires. The debt that Washington carries today has no such plan. It has an assumption that the next generation will find the money.

What the Constitution says

Article I, Section 8, Clause 2 gives Congress the power "To borrow Money on the credit of the United States." Article I, Section 9, Clause 7 says "No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law." The power to borrow belongs to the branch closest to the voters. Borrowing is a decision of the people's representatives, and the people have a right to know the figure. The live count is on the national debt clock, and I recommend you check it against the Treasury's Debt to the Penny page for yourself.

The way to take back the argument is to remove the abstraction. Forty trillion is a number that numbs. $6.86 billion a day is a number that insults. $400 billion for every point of interest is a number that sits in your wallet.

The case in brief

1. The total public debt rose from $38.05 trillion on November 4, 2025 to $40.56 trillion on November 5, 2026, an increase of $2.51 trillion in 366 days, or about $6.86 billion a day.
2. Divided among about 135 million households, the one-year increase is about $18,600 each and the whole debt about $300,000 each, as a way of seeing scale and not a bill in the mail.
3. Each percentage point of average interest on $40 trillion costs $400 billion a year, and the average rate moves slowly as old debt is refinanced.
4. Interest is a first claim on the budget, so as it rises it crowds out programs Congress can adjust or forces more borrowing.
5. The ratio argument, the reserve-currency argument and the hope of lower rates are each partial comforts, and none replaces a plan to stop adding to the debt.

What you can do: open the Treasury's Debt to the Penny page, write down today's total, and send it to your representative with a one-line question about which budget line he will cut or which tax he will change to slow it.