Mateo Castillo-Ruelas appeals the total 324-month sentence imposed after a jury convicted him of conspiracy to possess with the intent to distribute 100 kilograms or more of marijuana, illegal reentry after having previously been deported, and being a felon in possession of a firearm. Castillo-Ruelas argues that the district court erred in calculating the drug quanti *407 ty and in imposing an enhancement for obstruction of justice.

The district court’s calculation of the quantity of drugs involved in an offense is a factual determination that we review for clear error. United States v. Betancourt, 422 F.3d 240, 246 (5th Cir. 2005). Castillo-Ruelas’s mere opinion that his brother’s testimony was not credible is not sufficient to undermine the district court’s credibility determinations or rebut the reliability of the drug quantity information contained in the presentenee report (PSR). See United States v. Montes, 602 F.3d 381, 384 (5th Cir. 2010); United States v. Ford, 558 F.3d 371, 376-77 (5th Cir. 2009); United States v. Alford, 142 F.3d 825, 832 (5th Cir. 1998).

The district court’s determination that a defendant obstructed justice pursuant to U.S.S.G. § 3C1.1 is also a factual finding that we review for clear error. United States v. Juarez-Duarte, 513 F.3d 204, 208 (5th Cir. 2008). Castillo-Ruelas’s mere objection to the obstruction of justice enhancement, without more, does not suffice to rebut the truth, accuracy, or reliability of the supporting evidence contained in the PSR. See id. at 208; see also Ford, 558 F.3d at 376-77.

The district court did not clearly err in calculating the drug quantity or in imposing an obstruction of justice enhancement. See Betancourt, 422 F.3d at 246; Juarez-Duarte, 513 F.3d at 208. Accordingly, the judgment of the district court is AFFIRMED.