How long does the US Supreme Court take to make a decision after it hears a case?

According to an information guide for Supreme Court law clerks, the average time from argument to decision is approximately 81 days, except for cases heard on an emergency basis.

The guidebook warns this number is skewed by administrative decisions that may take only a few days. Other cases are beset by unavoidable delays attributed to the rules of the court and procedural and substantive due process (requests from one of the parties for extensions, enlargement of the record, etc.).

Occasionally, a non-emergent case may be decided in as few as 21 days, or, on rarer occasions may carry into the next Term due to reargument.

A survey of cases argued in the 2008-2009 Term revealed a few decisions delivered as quickly as five weeks after oral arguments, one delivered 26 weeks afterward, and another delivered slightly more than 30 weeks afterward. The majority of rulings seemed to fall in the range of 14-16 weeks after oral arguments.