Using Falconer’s formula (Falconer et al., 1996) heritability can be calculated as twice the difference between monozygotic and dizygotic twin correlation (rmz and rdz, respectively), as shown in Equation 1.
Analysis of Heritability Using Genome-wide Data Jacob B. Hall and William S. Bush(Author manuscript)Curr Protoc Hum Genet. 2016 Oct 11; 91: 1.30.1–1.30.10. doi: 10.1002/cphg.25
GCTA: A Tool for Genome-wide Complex Trait Analysis. The American Journal of Human Genetics Volume 88, Issue 1, 7 January 2011, Pages 76-82 (Open access) There has not been any consensus on the explanation of the “missing heritability.” Possible explanations include a large number of common variants with small effects, rare variants with large effects, and DNA structural variation.
For quantitative traits, heritability can be estimated as 2(rMZ − rDZ) where rMZ refers to the co-twin phenotypic correlation for MZ twins and rDZ refers to the correlation for DZ twins.