This tool will calculate the broad-sense heritability for your trait of interest using a set of wild isolates. The broad-sense heritability is the amount of trait variance that comes from genetic differences in the assayed group of strains. Generally, it is the ratio of genetic variance to total (genetic plus environmental) variance.
To obtain the best estimate of heritability, please measure a set of at least five wild strains in three independent assays. These assays should use different nematode growths, synchronizations, bacterial food preparations, and any other experimental condition. You should measure trait variance across as many different experimental conditions (in one block) as you would typically encounter in a large experiment.
Broad- and narrow-sense heritability are calculated using scripts available here.