How Many Justices Are on the Supreme Court? Nine, and Why

Short answer

• Nine justices sit on the U.S. Supreme Court: one Chief Justice of the United States and eight Associate Justices (28 U.S.C. § 1).
• The Constitution does not set the number. Article III establishes the Court; Congress fixes its size by ordinary statute.
• The size changed repeatedly between 1789 and 1869, ranging from an authorized low of five (never reached) to a high of ten.
• The Judiciary Act of 1869 set the Court at nine, one justice for each federal judicial circuit, and no statute has changed it since.
• Reductions worked by attrition. Because justices hold office during good behavior, Congress shrank the Court only by leaving seats empty as they fell vacant.
• Six justices form a quorum. Separately, by the Court's own practice known as the Rule of Four, four votes are enough to grant review of a case.

Introduction

The answer is nine. It has been nine since 1869, which is long enough that most Americans assume the number is written into the Constitution. It is not.

The Constitution creates “one supreme Court” and then falls silent on how many justices sit on it. Congress filled that silence by statute, and for the first 80 years of the republic it changed its mind again and again: six justices, then a planned five, then seven, nine, ten, a scheduled shrink to seven, and finally nine again. Each change tracked the growth of the federal court system, and several were openly political. The number survived its most famous attack in 1937, when President Franklin D. Roosevelt tried to expand the Court and lost. It is debated again today.

This article explains where nine comes from, how the number moved, why it stopped moving, and how the modern arguments for changing it are framed by the people who make them.

The Constitution Does Not Pick a Number

Article III, Section 1 of the Constitution provides:

“The judicial Power of the United States, shall be vested in one supreme Court, and in such inferior Courts as the Congress may from time to time ordain and establish.”

That is all. The text names the institution, gives its judges tenure “during good Behaviour,” and protects their salaries from being reduced while in office. It says nothing about how many judges the Court should have, how old they must be, or even that they must be lawyers. Those details were left to Congress, which has used the power from the very first session.

So the real answer to “how many justices are on the Supreme Court” has two layers. Today: nine. In principle: however many Congress says, which is why the history below is a history of statutes, not amendments.

How the Number Changed, 1789 to 1869

The Federal Judicial Center’s legislative history of the Court records the full sequence. Early changes followed the federal judicial circuits. In the Court’s first century, justices were expected to “ride circuit,” traveling to sit on the lower federal courts, so the size of the bench roughly tracked the number of circuits as the country grew.

Year	Law	Authorized size	What happened
1789	Judiciary Act of 1789	6	The first Court: a Chief Justice and five Associate Justices.
1801	Judiciary Act of 1801	6, dropping to 5 at the next vacancy	The outgoing Federalist Congress scheduled a reduction to limit the incoming president, Thomas Jefferson, but no seat fell vacant in time.
1802	Repeal of the 1801 act	6	Jefferson’s Congress repealed the reduction before it ever took effect.
1807	Act of February 24, 1807	7	A seventh seat added alongside a new judicial circuit.
1837	Act of March 3, 1837	9	Two seats added as new circuits were created for the growing South and West.
1863	Tenth Circuit Act	10	A tenth seat for the new Pacific circuit; President Abraham Lincoln appointed Stephen J. Field.
1866	Judicial Circuits Act	10, shrinking to 7 by attrition	Congress barred filling vacancies until the associate justices fell to six. Two seats lapsed, the Court reached eight, and President Andrew Johnson was denied any appointment.
1869	Judiciary Act of 1869	9	A Chief Justice and eight associates, matching the nine circuits. Unchanged ever since.

Politics was there from the start

The 1801 reduction was scheduled by a Congress and president about to hand power to their opponents, and it was understood at the time as a way to delay Jefferson’s first appointment. The 1860s were blunter. Congress raised the Court to ten in 1863, during the Civil War, which allowed Lincoln to appoint a justice expected to support the Union cause. In 1866, a Republican Congress hostile to President Andrew Johnson voted to shrink the Court toward seven specifically so that Johnson could not fill vacancies. The Senate’s own historical office notes that the act “blocked President Andrew Johnson’s appointment” and removed his chance to fill the next two vacancies. When Ulysses S. Grant, acceptable to Congress, became president in 1869, Congress restored the Court to nine.

Not every change was a power play. The expansions of 1807, 1837 and 1863 also answered a genuine workload problem: new states and territories meant new circuits, and each circuit was supposed to have a justice attached to it. Historians quoted in the 2021 Presidential Commission’s report note that some of the era’s changes were driven by “practical and mundane performance goals,” including keeping the Court at a workable, odd number that could not tie.

Why reductions could only shrink slowly

A president cannot fire a justice, and Congress cannot remove one by statute. Justices hold their offices during good behavior, which in practice means for life unless they retire, resign, die, or are impeached and convicted. So when Congress wanted a smaller Court, the only lawful lever was the empty chair: declare that the next vacancies simply would not be filled.

The 1801 plan relied on that mechanism, and it failed because nobody left. The 1866 act used it more successfully: Justice John Catron’s seat was already vacant when the act passed and was abolished in effect, and when Justice James Moore Wayne died in 1867 a second seat lapsed. The Court was down to eight and heading for seven when the 1869 act stopped the shrink and fixed the number at nine. Increases, by contrast, take effect immediately, because a new seat can be filled as soon as the president nominates and the Senate confirms.

The reason for the link to the circuits quietly disappeared

Nine endured for another reason too: the workload logic that produced it faded away without anyone needing to revisit the number. Congress created separate circuit judgeships in 1869, added new courts of appeals in 1891, and abolished the old circuit courts in 1911, so justices were gradually relieved of the travel that had once made the bench’s size a map of the country. By the time circuit riding was history, nine had simply become the familiar shape of the Court, and proposals to move off it, including enlargements floated in the 1870s and afterward, went nowhere.

1937: The Court-Packing Plan and Why It Failed

The most serious attempt to change the number since 1869 came on February 5, 1937. Fresh from a landslide re-election, President Franklin D. Roosevelt asked Congress for the Judicial Procedures Reform Bill. During his first term the Court had struck down centerpiece New Deal laws, including the National Industrial Recovery Act in 1935 and the Agricultural Adjustment Act in 1936. Roosevelt’s bill would have let him appoint one additional justice for every sitting justice over the age of 70 who did not retire, up to six additional justices. Six justices were then over 70, so the Court could have grown from nine to fifteen.

Roosevelt defended the plan publicly as an efficiency measure, arguing in his message to Congress that “aged or infirm judges” were slowing the courts. Critics in both parties called it what it looked like: an attempt to change the Court’s decisions by changing its membership, and they named it the “court-packing plan.” Chief Justice Charles Evans Hughes wrote to Senator Burton Wheeler of the Judiciary Committee that the Court was fully abreast of its work, which undercut the workload argument. On June 14, 1937, the committee issued a report condemning the bill as a “needless, futile and utterly dangerous abandonment of constitutional principle.”

Three things then happened in quick succession. On March 29, 1937, the Court upheld a Washington state minimum wage law in West Coast Hotel Co. v. Parrish, with Justice Owen Roberts joining the majority, a reversal of the Court’s recent pattern that was quickly nicknamed “the switch in time that saved nine.” Historians note that Roberts’s conference vote in the case had been cast in December 1936, weeks before Roosevelt announced the plan, so the famous switch was not, on the record, a response to it. In May, Justice Willis Van Devanter, one of the justices most opposed to the New Deal, announced his retirement, giving Roosevelt his first appointment. And on July 22, 1937, the Senate voted 70 to 20 to send the bill back to committee, killing it for good; its floor leader, Majority Leader Joseph Robinson, had died the week before.

The plan failed, but the Court changed anyway. Through retirements and deaths, Roosevelt went on to appoint eight new justices and to elevate Justice Harlan F. Stone to Chief Justice, remaking the Court’s majority within a few years, all without a single new seat.

Living With Nine: Quorum and the Rule of Four

The current statute, 28 U.S.C. § 1, carries forward the 1869 language: “The Supreme Court of the United States shall consist of a Chief Justice of the United States and eight associate justices, any six of whom shall constitute a quorum.” Six is therefore the minimum number who must participate for the Court to decide a case in the ordinary way, which is one reason a prolonged vacancy matters even though eight justices can still sit.

Separate from the statute is the Court’s own working rule for choosing cases. By long-standing practice, if four justices vote to grant a petition for certiorari, the case is heard. This “Rule of Four” is a custom of the Court, not a law, and it means a minority of the bench can put a question on the docket even though it takes five votes to decide it.

The Modern Debate: Expansion and Term Limits

Because the number is statutory, changing it requires only an ordinary act of Congress signed by the president (or passed over a veto). Bills to expand the Court have been introduced in recent Congresses, none has passed, and the argument continues. In April 2021 President Joseph Biden created the Presidential Commission on the Supreme Court of the United States, a bipartisan body of legal scholars charged with analyzing the debate rather than recommending outcomes. Its final report, issued in December 2021, took no position. It is the most useful neutral map of the modern arguments.

On expansion, supporters argue, in the Commission’s summary of their position, that the appointment process has become a high-stakes lottery in which the timing of deaths and retirements gives some presidents several appointments and others none, and that a larger Court would reduce the weight of any single seat and could better match the Court’s composition over time to the outcomes of national elections. Opponents argue that expansion would damage the Court’s legitimacy and independence, and would invite retaliation: each new majority could expand the Court again when it disliked the results, turning the bench into a continuing prize of electoral politics. The Commission recorded “profound disagreement” on expansion and warned that its risks are considerable.

On term limits, the leading proposal would give each justice a single non-renewable term of 18 years, staggered so that one seat opens every two years and each president appoints two justices per four-year term. Supporters argue this would regularize appointments, lower the temperature of confirmation fights, and end strategically timed retirements. Opponents argue that life tenure is what insulates justices from political pressure, and that fixed terms might make the Court more political, not less. There is also a genuine legal dispute, which the Commission noted its members were divided on: whether Congress could impose term limits by statute, given the Constitution’s “good Behaviour” tenure clause, or whether that change would require a constitutional amendment. The Commission found “considerable, bipartisan support” for term limits among the scholars and witnesses it surveyed, making them the most broadly supported of the major reforms it examined, and still it made no recommendation.

The Commission also examined other structural ideas, including panels drawn by rotation from the courts of appeals and a return to requiring justices to ride circuit, and recorded arguments on all sides without endorsing any of them. Those proposals share the same obstacle as expansion and term limits: each is an argument about how much of the Court’s current shape is essential to its independence and how much is simply inherited habit.

Both debates run into the same historical fact: nine is not protected by anything except 157 years of practice and the political cost of being seen to move first. The 1869 settlement has lasted not because it cannot be changed, but because every attempt to change it since, most visibly in 1937, has been judged in public as an attempt to control decisions rather than to fix the institution.

Frequently Asked Questions

Is the number of justices in the Constitution?

No. Article III creates the Supreme Court but never states its size. Congress sets the number by statute, and the current figure of nine comes from the Judiciary Act of 1869.

Who is the ninth justice, the Chief Justice?

The nine consist of one Chief Justice of the United States and eight Associate Justices. The Chief Justice is the Court’s presiding officer, but in deciding cases his vote counts the same as every other justice’s: one of nine.

Has the Supreme Court always had nine justices?

No. It began with six in 1789 and the authorized size moved repeatedly, reaching ten in 1863 and starting a shrink toward seven in 1866, before settling at nine in 1869, where it has remained.

Could Congress change the number today?

Yes, as a legal matter: an ordinary statute could set a different number, as Congress did several times in the 1800s. Whether it should is a live political debate. Expanding the Court is the most contested version; term limits attract broader support but raise their own constitutional questions.

What happens if a seat is empty for a long time?

The Court sits with eight justices (or fewer). Six justices are a quorum, so business continues, but an evenly divided eight-justice Court cannot set a national precedent in a split case: a 4 to 4 tie leaves the lower court’s decision standing, without a ruling on the merits for the rest of the country.

Why an odd number?

Nine is odd, which prevents tie votes on a full bench. That benefit is real but incidental historically: the 1869 act set nine mainly to match the nine federal judicial circuits then in existence. The tie-avoidance argument is one of the reasons given today for keeping an odd number.

Can a president add a justice whenever they want?

No. A president can only nominate someone to a seat that exists and is empty. Filling a vacancy requires a nomination by the president and confirmation by the Senate, and creating an entirely new seat first requires Congress to pass a law authorizing it, which is exactly the step that failed in 1937.

Conclusion

Nine is a statute, not a commandment. Congress chose it in 1869 to match the map of the federal circuits, after 80 years in which the size of the Court went up and down with the country’s growth and its politics. It failed to be changed in 1937 because the change was proposed in a way the public and the Senate read as an attack on the Court’s independence. And it remains changeable today by the same ordinary lawmaking that set it, which is exactly why the modern debate over expansion and term limits is really a debate about norms: the number is easy to alter on paper, and hard to alter without paying the price that Roosevelt paid.

Keep reading: Due Process, the Bill of Rights and the 10th and 14th Amendments: Explained in Plain English

Sources & references

• Federal Judicial Center (fjc.gov), "Supreme Court of the United States: Legislative History": dates, citations and effect of the acts of 1789, 1801, 1802, 1807, 1837, 1863, 1866 and 1869, and authorized sizes.
• 28 U.S.C. § 1 (via Legal Information Institute, Cornell, law.cornell.edu): "The Supreme Court of the United States shall consist of a Chief Justice of the United States and eight associate justices, any six of whom shall constitute a quorum."
• U.S. Senate (senate.gov), "Nominations: A Historical Overview" and "About the Supreme Court": the 1866 act's effect in blocking President Johnson's appointments; the 1869 reversal under President Grant.
• Supreme Court of the United States (supremecourt.gov), "About the Court" and Court history materials: composition of one Chief Justice and eight Associate Justices; the size set by Congress.
• National Constitution Center (constitutioncenter.org), Constitution 101 Info Brief 9.1, "Supreme Court": Congress altered the size six times, most recently in 1869.
• Encyclopaedia Britannica (britannica.com), "Why Are There Nine Justices on the U.S. Supreme Court?": the 1866 reduction and its political context.
• Franklin D. Roosevelt Presidential Library and Museum (fdrlibrary.marist.edu): the February 5, 1937 proposal and message to Congress; Senate Judiciary Committee report of June 14, 1937.
• Presidential Commission on the Supreme Court of the United States, Final Report (December 2021, Executive Order 14023): analysis of the arguments for and against expansion and term limits; no recommendation made.