Calculate broad- and narrow-sense heritability, twin-study variance components, and breeder's equation values from genetic data.

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Heritability describes variation in a specified population and environment, not the genetic share of an individual trait. These are simplified models.

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Heritability Coefficient Formula

The following formula gives broad-sense heritability from total genetic variance and phenotypic variance. Narrow-sense heritability instead uses additive genetic variance. All variance values must use the same population, study conditions and squared trait units.

H² = Vg / Vₜ

Variables:

  • H² is the broad-sense heritability coefficient
  • V_g is the variance due to genetics
  • V_t is the total variance

To calculate the heritability coefficient, divide the variance due to genetics by the total variance. This ratio represents the genetic variance proportion under the specified variance-component model; V_t must be positive and V_g must lie between zero and V_t. Narrow-sense h² = V_a / V_t uses additive variance.

What is Heritability Coefficient?

The heritability coefficient is a measure used in genetics to quantify the extent to which genetic factors contribute to the variance in a particular trait within a population. It is expressed as a ratio of the variance due to genetics to the total variance observed in the trait. A higher heritability coefficient indicates that a larger proportion of the variance in the trait is due to genetic differences among individuals, while a lower coefficient suggests that environmental factors play a more significant role. Heritability coefficients are commonly used in studies of traits such as height, intelligence, and susceptibility to certain diseases. They describe variation in a particular population and environment, not the genetic share of an individual trait or whether a trait can change. The twin mode uses the simplified ACE equations a² = 2(rMZ−rDZ), c² = 2rDZ−rMZ and e² = 1−rMZ; raw components outside 0–1 are flagged without clamping. The breeder’s equation R = h²S uses narrow-sense heritability and consistent trait units; when means are selected, S is the selected-parent mean minus the population mean. These modes rely on model assumptions. See a primary twin-study application and a primary study of heritability and selection response.

How to Calculate Heritability Coefficient?

The following steps outline how to calculate the Heritability Coefficient.

  1. First, determine the variance due to genetics (V_g).
  2. Next, determine the total variance (V_t).
  3. Finally, calculate the heritability coefficient using the formula H^2 = V_g / V_t.
  4. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Variance due to genetics (V_g) = 20

Total variance (V_t) = 50

Broad-sense H² = 20 / 50 = 0.4, or 40%. In the simple independent V_t = V_g + V_e partition, the non-genetic remainder is 30 (60%); a fuller model may require covariance or interaction terms.