Phenotypic ratio pertains to the relative number of offspring manifesting a particular trait or combination of traits. It can be determined by doing a test cross and identifying the frequency of a trait or trait combinations that will be expressed based on the genotypes of the offspring.
For example: when a tall plant is crossed to a short plant, some of their offspring will be tall while others will be short. To determine the phenotypic ratio, the number of times the phenotypes (either tall or short) are expressed is counted. In this case, the phenotypic ratio shall indicate how many of the offspring will be tall and how many will be short based on the genotype.