Densidade Efetiva (Ne)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The effective population size (Ne) calculator estimates the number of individuals contributing genetically to the next generation. This metric accounts for imbalances in reproductive sex ratios, fertility variation, and population fluctuations that reduce genetic diversity. It's critical for conservation biology and population genetics to assess inbreeding risks and adaptive potential.
The approximation formula adjusts total population size (Ne) using reproductive sex ratios and seasonal variations. For example, if a population has 200 individuals but only 40% are reproductive females, Ne will be significantly lower. The calculator applies formulas like Ne = 4×Nm×Nf/(Nm + Nf) for sex imbalances, providing a more realistic estimate.
Use this tool for conservation planning, endangered species assessments, or modeling environmental impacts. Note: the result is an approximation. Populations with genetic flow between subpopulations or strong natural selection may require more complex methods. Always validate data with direct genetic analyses where possible.
Frequently asked questions
Why is effective population size lower than total individuals?
Because it considers only reproductive individuals and accounts for fertility variation, excluding sex ratio imbalances and population fluctuations.
How does the calculation handle sex ratio imbalances?
The calculator uses Ne = 4×Nm×Nf/(Nm + Nf), where Nm and Nf are reproductive males and females, providing an adjusted estimate.
Can I use this tool for species with non-random mating?
Yes, but accuracy may decrease. The calculator assumes random mating and doesn't account for forced inbreeding or mate selection patterns.
What if the population has constant size over time?
For stable populations, theoretical Ne matches the calculated effective size. For growing populations, use the geometric mean of annual sizes.