A two-thirds majority vote means at least 66.7% of those voting must agree. The U.S. Constitution sets this bar for a short list of high-stakes decisions — overriding a presidential veto, proposing amendments, ratifying treaties, convicting an impeached official, expelling a member of Congress, and overruling a President who disputes being declared unable to serve. Private organizations and corporations use the same threshold in their own rules, most often through Robert’s Rules of Order or charter supermajority provisions. Two-thirds majority vote requirements almost always apply to members present and voting, not to the full membership, which is the single most misunderstood part of the rule.
Where a Two-Thirds Vote Is Required
- Overriding a presidential veto: two-thirds of each chamber of Congress (Article I, Section 7)
- Proposing a constitutional amendment: two-thirds of each chamber, or a convention called by two-thirds of state legislatures (Article V)
- Ratifying a treaty: two-thirds of Senators present (Article II, Section 2)
- Convicting an impeached official: two-thirds of Senators present (Article I, Section 3)
- Expelling a member of Congress: two-thirds of the relevant chamber (Article I, Section 5)
- Overruling a President who disputes a disability declaration: two-thirds of both chambers (25th Amendment, Section 4)
- Motions that limit member rights under Robert’s Rules of Order: two-thirds of votes cast
- Major corporate actions where the charter says so: typically 67% to 90% of shareholders, as the governing documents specify
One point of frequent confusion: ending a Senate filibuster through cloture takes three-fifths of all Senators (60 votes), not two-thirds. That number was reduced from two-thirds in 1975.1United States Senate. About Filibusters and Cloture
How To Calculate a Two-Thirds Vote
The math itself is simple. Two-thirds of 100 Senators is 67. Two-thirds of 435 House members is 290. But those figures only apply if every seat is filled and every member votes, and most two-thirds requirements in the Constitution don’t work that way.
The important distinction is between two-thirds of total membership and two-thirds of those present and voting. The Supreme Court has held that a veto override requires two-thirds of a quorum, not two-thirds of the entire body.2Congress.gov. ArtI.S7.C2.2 Veto Power The same rule applies to proposing constitutional amendments: two-thirds of members present, with a quorum, is enough.3Congress.gov. ArtV.1 Overview of Article V, Amending the Constitution If only 60 Senators are present for such a vote, 40 yes votes clear the bar.
Under Robert’s Rules of Order, abstentions don’t count toward the calculation either. The threshold applies only to actual votes cast. A quick check: if the yes votes are at least double the no votes, two-thirds has been reached.4Robert’s Rules of Order. FAQs Thirty no votes require at least 60 yes votes, no matter how many people abstained.
Corporate supermajorities are the exception. Those are typically written against outstanding shares entitled to vote rather than shares actually voted, so absent shareholders effectively count as no votes. The exact wording lives in the company’s charter or bylaws.
Overriding a Presidential Veto
When the President vetoes a bill, Congress can still enact it by passing the bill again with a two-thirds vote in both chambers. The Presentment Clause in Article I, Section 7 lays out the procedure: the originating chamber votes first to pass the bill over the President’s objections, and if it reaches two-thirds, the bill moves to the other chamber, which must also clear two-thirds.2Congress.gov. ArtI.S7.C2.2 Veto Power Overrides are uncommon because the President’s own party typically holds enough seats in at least one chamber to block the threshold.
Proposing Constitutional Amendments
Article V provides two paths for proposing amendments. The first, and the only one ever used, requires two-thirds of members present in both the House and Senate to approve a proposed amendment before it goes to the states.3Congress.gov. ArtV.1 Overview of Article V, Amending the Constitution The second path lets two-thirds of state legislatures — 34 of the 50 today — apply to Congress, which then must call a convention for proposing amendments.5Congressional Research Service. The Article V Convention for Proposing Constitutional Amendments: Historical Perspectives for Congress Any amendment coming out of either path still needs ratification by three-fourths of the states (38) to take effect.
Ratifying Treaties
Under Article II, Section 2, the President negotiates treaties, but a treaty does not take effect until two-thirds of the Senators present approve it.6Congress.gov. ArtII.S2.C2.1.1 Overview of the Treaty Power The vote is on a resolution of ratification; formal ratification happens later, when instruments are exchanged between the United States and the other nation.7United States Senate. About Treaties A determined Senate minority can therefore block any international agreement.
Convicting an Impeached Official
Impeachment runs in two steps. The House impeaches a federal official — the President, a federal judge, a cabinet member — by simple majority, which works like an indictment. The Senate then holds a trial, and conviction and removal require two-thirds of the Senators present.8Constitution Annotated. Article I Section 3 Clause 6 – Impeachment Trials No President has ever been convicted by the Senate. The two-thirds threshold means a meaningful number of the President’s own party must break ranks, and that is typically where impeachment efforts have stalled.9United States Senate. About Impeachment
Expelling a Member of Congress
Each chamber can expel one of its own members by two-thirds vote under Article I, Section 5.10United States Senate. About Expulsion This is separate from impeachment, which reaches executive officials and federal judges. Expulsion has happened roughly 20 times in American history, with most cases tied to support for the Confederacy during the Civil War.
Presidential Disability Under the 25th Amendment
Section 4 of the 25th Amendment, ratified in 1967, sets up a procedure for when a President becomes unable to serve. If the Vice President and a majority of the cabinet declare the President unable to carry out the duties of office, the Vice President becomes Acting President. If the President disputes that declaration, Congress decides, and keeping the President sidelined over that objection requires a two-thirds vote of both chambers within 21 days.11Constitution Annotated. Twenty-Fifth Amendment Falling short of two-thirds returns power to the President. The provision has never been invoked.
Two-Thirds Votes Under Robert’s Rules of Order
Many private organizations run meetings under Robert’s Rules of Order. Under those rules, any motion that limits members’ rights or reverses a previous decision needs a two-thirds vote. The reasoning tracks the constitutional pattern: actions that curtail what members can do should not pass on a bare majority.
Motions that require two-thirds approval include closing debate (also called “calling the question,” which forces an immediate vote on the pending matter); limiting debate to a set time or number of speakers; tabling a motion in order to kill it rather than merely postpone it; and rescinding a previous action when no prior notice was given. If members were given prior written notice that a rescission would be proposed, a simple majority suffices.
Supermajority Provisions in Corporate Governance
Corporate supermajorities work differently. They are not the default. Under the Delaware General Corporation Law, which governs more publicly traded companies than any other state’s code, a simple majority of outstanding shares approves most major transactions. Mergers require a majority of outstanding stock entitled to vote.12Delaware Code Online. Delaware Code Title 8 – General Corporation Law Dissolution also requires a majority of outstanding stock.13Justia Law. Delaware Code Title 8 Section 275 – Dissolution Generally
Companies can raise the bar in their certificates of incorporation or bylaws. Delaware law lets a corporation specify the votes required for any business transaction, provided the quorum is not set below one-third of shares entitled to vote.14Justia Law. Delaware Code Title 8 Section 216 – Quorum and Required Vote for Stock Corporations Many companies adopt supermajority provisions requiring 67% or more of shareholder approval for mergers, acquisitions, or amendments to the charter itself. These provisions function as anti-takeover defenses: a hostile acquirer who assembles a bare majority still cannot force a merger through if the charter demands two-thirds.
Changing or removing a supermajority provision usually requires the same supermajority vote, which makes these provisions sticky once adopted. Before investing, check the charter and bylaws for these requirements. They shape how much influence any single large shareholder can have over the company’s direction.