Model breeding structure using multiple effective size formulas. Review assumptions, results, exports, and visual trends. Understand genetic drift risk from changing breeding population patterns.
Choose a method that matches your biology dataset. The calculator supports sex ratio, family-size variance, fluctuating census history, and inbreeding-rate estimation.
The chart updates after calculation and visualizes how the selected method responds to the main input variable.
This sample dataset shows how different population-genetic inputs produce different effective population sizes.
| Method | Inputs | Formula | Example Ne |
|---|---|---|---|
| Sex ratio | Nm = 60, Nf = 40 | 4NmNf / (Nm + Nf) | 96.00 |
| Family-size variance | N = 120, Vk = 6 | (4N - 2) / (Vk + 2) | 59.75 |
| Harmonic mean | 120, 80, 60, 140 | t / Σ(1/Ni) | 89.60 |
| Inbreeding rate | ΔF = 0.01 | 1 / (2ΔF) | 50.00 |
Ne = (4NmNf) / (Nm + Nf)
This method estimates effective size when the number of breeding males and breeding females differs. The result drops as the sex ratio becomes more uneven.
Ne = (4N - 2) / (Vk + 2)
This method is useful when some parents contribute many offspring while others contribute few. Greater reproductive inequality usually reduces effective population size.
Ne = t / Σ(1 / Ni)
This method is designed for populations that change in size across generations. Short bottlenecks matter strongly because small generations weigh heavily in the harmonic mean.
Ne = 1 / (2ΔF)
This method estimates effective size from the per-generation increase in inbreeding. Higher inbreeding growth implies a smaller effective population.
Choose a method matching your data. Use sex counts, family-size variance, fluctuating generation sizes, or the inbreeding rate. The calculator applies the selected formula and returns Ne, optional Ne/N, and a comparison graph.
Not all individuals breed equally. Uneven sex ratios, reproductive skew, bottlenecks, and drift reduce how many genomes are effectively transmitted to the next generation.
Use it when breeder counts for males and females are known and generations are reasonably discrete. It is common in breeding management and conservation planning.
It measures how unequal offspring production is among parents. When a few individuals produce most descendants, genetic drift increases and effective population size falls.
It captures the outsized effect of population bottlenecks. Very small generations reduce long-term effective size more strongly than large generations increase it.
If you know the per-generation inbreeding increase, Ne equals 1 divided by twice ΔF. Larger ΔF values indicate smaller effective populations.
Yes. Change breeder counts, reproductive variance, or generation histories and compare the returned Ne values to test alternative breeding or conservation plans.
Use counts of individuals for N, Nm, Nf, and generation sizes. Use a unitless variance for Vk and a decimal per-generation rate for ΔF.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.