Roberto Arteaga-Mendez pleaded guilty to one count of conspiracy to distribute methamphetamine. In the written plea agreement, Arteaga-Mendez stipulated that he was responsible for between 500 grams and 1.5 kilograms of methamphetamine. Based on this drug quantity, the district court * sentenced Arteaga-Mendez to 135 months in prison, fifteen months more than the statutory mandatory minimum sentence.

Arteaga-Mendez appeals his sentence, arguing the Government failed to establish a factual basis for his plea. Based on Arteaga-Mendez’s responses during the plea colloquy, the written plea agreement, and the agreement’s stipulation of facts, however, the district court could reasonably decide Arteaga-Mendez likely committed the offense. See United States v. Gamble, 327 F.3d 662, 664 (8th Cir. 2003). Although he made no objection in the district court, Arteaga-Mendez also 'challenges the district court’s finding of drug quantity. The district court did not commit plain error because its drug quantity finding is based on Arteaga-Mendez’s drug quantity stipulation and the unchallenged drug quantity calculation contained *503 in the PSR. See United States v. Beatty, 9 F.3d 686, 690 (8th Cir. 1993). We note Arteaga-Mendez does not raise any argument under United States v. Booker, — U.S.-, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005).

We thus affirm Arteaga-Mendez’s sentence.