Jimmie Vance Grubbs pled guilty to six counts of knowingly transporting someone under the age of eighteen in interstate commerce with intent to engage in a sexual activity, in violation of 18 U.S.C. § 2423(a), and six counts of traveling in interstate commerce for the purpose of engaging in a sexual act with a person under the age of eighteen, in violation of 18 U.S.C. § 2423(b). The district court sentenced Grubbs to 240 months of imprisonment and a life term of supervised release. On appeal, Grubbs does not contest his convictions, but contends the district court erred in imposing his sentence for three reasons: (1) the district court violated his Sixth Amendment rights by considering uncharged conduct when deciding an appropriate sentence; (2) the district court violated his Fifth Amendment rights by failing to require the Government to prove uncharged conduct by more than a preponderance of the evidence standard; and (3) the district court committed procedural errors in calculating his United States Sentencing Guidelines ("Guidelines") range. For the reasons that follow, we disagree with Grubbs and affirm the judgment of the district court.