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Calcimator

Population Viability Analysis Calculator

Estimate extinction probability from population size and environmental/demographic variability using diffusion approximation models.

Inputs

years

Results

Extinction Probability

84.53%

Viability Rating

Non-Viable (High Risk)

Expected Population at End479
Stochastic Growth Rate0.87%/yr
Mean Time to Extinction1 years
Total Variance2.26%
MVP (Short-Term, 50/500 Rule)50
MVP (Long-Term, 50/500 Rule)500
How to Use This Calculator
  1. Enter Current Population Size — use the most recent survey estimate with its uncertainty range.
  2. Set Mean Annual Growth Rate (lambda) from long-term monitoring data or published life-table analyses.
  3. Input Environmental Variability and Demographic Variability to capture stochastic extinction risk.
  4. Set Time Horizon (years) for the projection period (50 and 100 years are standard IUCN benchmarks).
  5. Enter Quasi-Extinction Threshold — the minimum population size considered functionally extinct.
  6. Review Extinction Probability (%) and Viability Rating to assess conservation status and prioritize intervention efforts.

How the result changes with Environmental Variability

Environmental VariabilityExtinction ProbabilityViability Rating
10%100%Non-Viable (High Risk)
35%74.13%Non-Viable (High Risk)
65%99.65%Non-Viable (High Risk)
90%100%Non-Viable (High Risk)

What each input means

Current Population Size
Total number of breeding individuals in the population.
Mean Annual Growth Rate
Average intrinsic growth rate as a percentage per year. Negative values indicate declining populations.
Environmental Variability
Year-to-year variation in growth rate due to environmental factors (drought, disease, etc.).
Demographic Variability
Random variation due to individual birth/death events. More significant for small populations.
Time Horizon
Number of years to project into the future for extinction risk assessment.
Quasi-Extinction Threshold
Population size below which the species is considered functionally extinct.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Current Population Size = 200, Mean Annual Growth Rate = 2, Environmental Variability = 15, Demographic Variability = 10 = 6 input(s) provided
  2. Calculate Extinction Probability
    Extinction Probability
    84.53 = 84.53
  3. Calculate Viability Rating
    Non-Viable (High Risk) = Non-Viable (High Risk)
  4. Calculate Expected Population at End
    Expected Population at End
    479 = 479
  5. Calculate Stochastic Growth Rate
    Stochastic Growth Rate
    0.87 = 0.87

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