Extinction Risk Calculator

Estimate a species' extinction probability using key population and threat parameters. Enter the current population size, population trend, geographic range size, generation length, habitat quality, and threat level to receive a calculated extinction risk score, an IUCN-style risk category, and a breakdown of contributing risk factors. Also try the Population Density Calculator.

Current Population Size (individuals) *

Estimated total number of mature individuals in the wild.

Population Trend (% change per decade) *

Negative values indicate decline; positive values indicate growth.

Generation Length (years) *

years

Average time between birth of individuals and birth of their offspring.

Geographic Range (km²) *

km²

Extent of occurrence or area of occupancy of the species.

Range Trend (% change per decade) *

Rate of change in the species' geographic range. Negative = shrinking.

Habitat Quality *

Primary Threat Level *

Number of Sub-populations *

Number of geographically or genetically distinct sub-populations.

Annual Reproductive Rate (offspring per individual) *

Average number of viable offspring produced per individual per year.

% of Range Under Legal Protection *

Percentage of the species' range within protected areas or reserves.

Results

Extinction Probability (100 years)

IUCN-Style Risk Category

Population Risk Score

Habitat & Range Risk Score

Threat Risk Score

Overall Risk Index (0–100)

What does the extinction probability percentage mean?

The extinction probability is an estimated likelihood that a species will become extinct within 100 years, expressed as a percentage. A value of 50% means there is roughly an equal chance the species will or will not persist to that time horizon under current conditions. This is a model-based estimate, not a guaranteed outcome. See also our calculate Selection Strategy Type, Final Population Size & Population Growth Rate — r and K Selection.

How does population size affect extinction risk?

Smaller populations are far more vulnerable to extinction due to demographic stochasticity, inbreeding, and reduced genetic diversity. Species with fewer than 250 mature individuals are generally considered critically endangered under IUCN criteria. The calculator weights smaller populations significantly higher in the overall risk score.

What IUCN categories does this calculator map to?

The calculator maps results to five IUCN-aligned categories: Least Concern (LC), Near Threatened (NT), Vulnerable (VU), Endangered (EN), and Critically Endangered (CR). These align broadly with IUCN Red List criteria A–D. The output is an approximation and should not replace a formal IUCN assessment.

Why does generation length matter for extinction risk?

Species with longer generation times recover more slowly from population declines because reproduction is less frequent. A species with a 50-year generation length facing a 30% population decline will take far longer to recover than one with a 1-year generation. This calculator incorporates generation length to adjust how quickly declines translate into extinction risk. You might also find our Mark-Recapture Calculator (Lincoln-Peterson) useful.

How is geographic range size used in the calculation?

A small geographic range concentrates risk — a single catastrophic event (disease, wildfire, storm) can eliminate the entire species. IUCN Criterion B considers ranges under 20,000 km² as a risk factor for Vulnerable status. Combined with range trend, a shrinking small range significantly elevates the extinction probability score.

Does the number of sub-populations affect risk?

Yes. A species split across many sub-populations is more resilient than one concentrated in a single location, as localized events are less likely to eliminate all sub-populations at once. Fewer sub-populations increase both vulnerability and the risk score. Species with only one sub-population face much higher extinction risk regardless of total population size.

What counts as a 'critical' threat level?

Critical threats are immediate, severe, and widespread factors actively driving the species toward extinction — such as ongoing habitat destruction affecting the entire range, unsustainable exploitation, invasive predators with no management response, or disease outbreaks. These are typically threats where, without immediate intervention, extinction within decades is plausible.

Can protected areas significantly reduce extinction risk?

Yes. Having a large proportion of the species' range under formal legal protection reduces exposure to habitat destruction, hunting, and other human pressures. The calculator applies a protection discount to the overall risk score — species with over 75% of their range protected receive a meaningful risk reduction, though protection alone does not eliminate all threats.