Animal Mortality Rate Calculator (flock or herd mortality % and livability)

Understanding the animal mortality rate calculator — concept and principle

Livestock and poultry producers track mortality to judge flock or herd health and compare batches. This calculator finds cumulative mortality, livability (survival), deaths per 1,000 animals placed and average daily and weekly mortality over a period.

Four deaths out of 100 placed is 4% mortality and 96% livability; spread over six weeks that is 0.67% a week.

How it is calculated

Cumulative mortality (%) = animals that died ÷ animals placed × 100.
Livability (%) = 100 − mortality.
Deaths per 1,000 placed = mortality % × 10.
Average mortality per day = cumulative mortality ÷ days; per week = per day × 7.
For herds that buy and sell animals during the period, divide by the average number present instead of the number placed.

The principle

Mortality is a proportion: of the animals at risk, how many died. Expressing it per day or per week lets you compare batches kept for different lengths of time, such as broiler flocks reared to different ages. Deaths do not occur evenly, though: they often cluster in the first week after placement and during disease outbreaks, so daily records reveal problems that an average hides.

Worked example

Default inputs: 100 animals placed, 4 died, period 42 days.

Mortality = 4 ÷ 100 × 100 = 4%.
Livability = 100 − 4 = 96%; animals still alive = 96.
Deaths per 1,000 placed = 40.
Average mortality per day = 4 ÷ 42 ≈ 0.09524%.
Average mortality per week = 0.09524 × 7 ≈ 0.67%.

How to read the result

Compare with your own past batches, breed or company standards and local benchmarks for the same species and production stage. A sudden rise in daily mortality is an early warning sign of disease, heat stress, ventilation or water problems and should prompt investigation with a veterinarian.

Common mistakes

Counting culled animals inconsistently (some records include them, others separate them).
Dividing by animals present at the end instead of the start.
Comparing cumulative mortality of batches kept for different lengths of time.
Relying on a weekly average that hides a spike.

Keep in mind: Mortality figures describe outcomes; they do not diagnose causes. Consult a veterinarian about unusual losses and follow local animal health rules.

Frequently asked questions

How do you calculate mortality rate in poultry?

Divide the number of birds that died by the number placed and multiply by 100.

What is livability?

The percentage of animals that survived the period: 100% minus cumulative mortality.

Should culls be included?

Decide one rule and use it consistently; many records report mortality and culls separately and also combined.

Sources: Thrusfield, M., Veterinary Epidemiology, 4th ed. Wiley-Blackwell (measures of mortality) · FAO, Good practices for biosecurity in the pig and poultry sectors

Checked 9 Nov 2026. Cornell University and Cornell Cooperative Extension (Allegany, Cattaraugus, Chautauqua, Erie and Steuben counties), fact sheet “Tracking Broiler Flock Performance”: % mortality = number of mortalities ÷ number of chicks ordered (placed) × 100. Livability = 100% − mortality and the per-day average are standard arithmetic.

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