Deciding a case at the Supreme Court takes a simple majority of the justices who participate. When all nine sit, that means five votes. The number of Supreme Court justices needed to decide a case is not fixed at five, though — it tracks whoever is actually hearing the case, so if a justice steps aside, the majority shrinks with the bench.
The Six-Justice Floor
Before any decision can happen, the Court needs a quorum. Federal law sets that floor at six of the nine justices.1Office of the Law Revision Counsel. 28 USC 1 – Number of Justices; Quorum The Court’s own guidance confirms the same figure and notes that justices who can’t attend arguments in person may still participate by reviewing transcripts and audio.2Supreme Court of the United States. Frequently Asked Questions – General Information
Losing a quorum is unusual and typically happens when several justices have conflicts in the same case. If it does, cases that came up through the normal appeals process end with the lower court’s ruling affirmed — the same limited outcome as a tie. For cases on direct appeal from a federal district court, the Chief Justice can instead send the matter to the appropriate federal circuit court for a final decision.3Office of the Law Revision Counsel. 28 US Code 2109 – Quorum of Supreme Court Justices Absent
A Majority of Whoever Is Sitting
The controlling rule is a majority of the participating justices. With nine, that is five votes, producing the familiar 5–4, 6–3, 7–2, 8–1, and 9–0 tallies.4United States Courts. Supreme Court Procedures A majority has to agree not just on which side wins but on the reasoning of the opinion before it is publicly released.
When a justice sits out, the math moves with the bench. Eight participating justices still need five for a majority. Seven need four. The rule is always more than half of whoever is hearing the case.
Recusals Shrink the Bench
Recusals are the usual reason the Court operates with fewer than nine. Federal law requires a justice to step aside in any situation where a reasonable person might question their impartiality, including a financial interest in a party, prior work on the matter as a lawyer or government official, or a close family member involved in the case.5Office of the Law Revision Counsel. 28 US Code 455 – Disqualification of Justice, Judge, or Magistrate Judge
There is no substitute justice. Unlike lower federal courts, which can reassign a case to a different judge, the Supreme Court simply proceeds with the justices who remain. One recusal rarely changes the outcome. Two or three start to matter, because a smaller bench means fewer votes to reach a majority and better odds of an even split.
What Happens When the Vote Ties
An even number of participating justices can split evenly, most often 4–4. When that happens, the lower court’s ruling stands.4United States Courts. Supreme Court Procedures The Court usually issues a brief order stating only that the judgment was “affirmed by an equally divided Court,” with no explanation of who voted which way.
A tie affirmance does not set a national precedent. The lower court’s decision governs the parties and remains binding only within that circuit. Other circuits stay free to rule the opposite way on the same question, which leaves the underlying legal issue open until the Court takes it up again with a full bench. Congress treats quorum-shortfall affirmances the same limited way.3Office of the Law Revision Counsel. 28 US Code 2109 – Quorum of Supreme Court Justices Absent
When a Majority Agrees on the Winner but Not the Reasoning
A case can have five votes for one side without five justices agreeing on why. That produces a plurality opinion: the opinion with the most votes, but short of a true majority.6United States Courts. Glossary – US v Alvarez Three justices might sign the lead opinion, two might concur in the result on different grounds, and four might dissent. The judgment goes 5–4, but no single legal rationale carries five votes.
Plurality decisions are still binding, but they are harder for lower courts to apply. Under the Supreme Court’s 1977 ruling in Marks v. United States, lower courts are supposed to treat the “narrowest grounds” shared by the justices who supported the judgment as the holding.7Library of Congress. Marks v United States, 430 US 188 (1977) Identifying those grounds is often contested, and courts have developed different approaches for reading fractured opinions.
Different Vote Counts for Different Actions
The majority rule governs deciding a case on the merits. Other steps use other numbers, and they are worth knowing so the “five of nine” answer is not applied where it does not fit.
- Agreeing to hear a case takes four votes under the Rule of Four, not five. The Court’s own rules explain that certiorari is granted only for compelling reasons, such as conflicting decisions among federal circuit courts.4United States Courts. Supreme Court Procedures8Legal Information Institute. Supreme Court Rules – Rule 10
- Granting an emergency stay from the full Court takes five votes, though a single Circuit Justice can act on an application alone or refer it to the full Court.9Supreme Court of the United States. A Reporters Guide to Applications Pending Before the Supreme Court
- Dismissing a case as improvidently granted after certiorari has been granted generally takes six votes, to keep a bare majority from undoing what four justices agreed to hear.
- A quorum for any business at all is six justices.1Office of the Law Revision Counsel. 28 USC 1 – Number of Justices; Quorum
So the short answer stays short: a majority of the justices who hear the case, usually five when the bench is full. The longer answer is that the number moves with recusals, an even split leaves the lower court’s ruling in place, and a five-vote majority does not always mean five votes for the same reasoning.