What is allele frequency?
Allele frequency describes how common a gene variant is within a population. In this calculator, the focus is a recessive-disease model where the observed disease frequency is used to estimate the mutant allele frequency.
The result is a population-level estimate. It should not be treated as a personal diagnostic result or a substitute for genetic counseling.
How to use the allele frequency calculator?
Choose whether disease occurrence is entered as a proportion or a percentage, then enter the occurrence value. The calculator estimates the healthy allele frequency p, mutant allele frequency q, and carrier frequency 2pq.
The occurrence value should represent the same population you want to analyze. Mixing data from different populations, disease definitions, or screening methods can distort the estimate.
How to calculate allele frequency?
For a recessive disease under Hardy-Weinberg assumptions, disease frequency is q squared. The mutant allele frequency q is the square root of that disease frequency, and the healthy allele frequency p is one minus q.
Carrier frequency is 2pq. The calculator also reports the reciprocal carrier frequency so the result can be read as an approximate one-in-N value.
What is the Hardy-Weinberg equation?
The Hardy-Weinberg equation is p squared plus 2pq plus q squared equals 1. It describes expected genotype frequencies when mating is random and the population is not affected by selection, mutation, migration, or genetic drift.
Real populations may not meet those assumptions exactly. Use the output as a model-based estimate and verify important interpretations with appropriate genetics expertise.