Gene expression report format TSV RPKM rpkm 1.25 For example a 1kb transcript with 1000 alignments in a sample of 10 million reads (out of which 8 million reads can be mapped) will have RPKM = 1000/(1 * 8) = 125 Tab-delimited format for gene expression levels table, calculated as Reads Per Kilobase per Million (RPKM) mapped reads. Gene expression levels table format