M13 is a filamentous phage that has attracted much attention in the field of molecular biology and biotechnology. It belongs to the family Inoviridae and mainly infects Escherichia coli (E. coli). M13 phage has a simple single-stranded DNA genome of about 6.4 kilobases and a rod-shaped morphology. M13 phage can display foreign peptides or proteins on its surface. By genetically engineering the M13 genome to include genes encoding proteins of interest in the phage coat protein genes, phage particles are generated that can display proteins on their surface. Phage titration ELISA is a technique used to determine the concentration or titer of phage (bacteriophage) particles in a given sample. The Phage Titration ELISA determines the relative number of phage particles and provides a rapid, sensitive and reproducible alternative method for titrating M13 phage preparations.