In order to prepare high quality double-stranded DNA libraries for Illumina WGS, extracted genomic DNA needs to be accurately quantified. Qubit Fluorometers detect fluorescent dyes that are specific to the target of interest. These fluorescent dyes emit only when bound to specific target molecules, even at low concentrations. This provides obvious advantages over UV absorbance quantitation, which measures anything absorbing at 260 nm \u2014 DNA, RNA, protein, free nucleotides, or excess salts. Moreover, UV spectrophotometry often does not have the sensitivity to accurately measure low concentrations of DNA and RNA. The Qubit dsDNA broad-range (BR) and high-sensitivity (HS) assays are highly selective for double-stranded DNA (dsDNA) over RNA and single-stranded DNA (ssDNA). This protocol has been adapted from dsDNA quantification assays developed by ThermoFisher Scientific.Variations of this method include quantification assays from Promega:DNA quantification using the Quantus fluorometerThis is an open-access protocol distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike.