Litter Size Predictor
Estimate expected litter size from breed size, age and parity.
About Litter Size Predictor
Litter size correlates with maternal body size in dogs but is fairly constant in cats. First litters run smaller and size declines after about seven years of age. A radiographic count near day 45 is the only reliable figure, and knowing it beforehand is what makes a retained fetus detectable during whelping.
Formula
Litter Size Predictor
Litter size scales with maternal body size, adjusted for age and parity
- parity
- Number of previous litters; first litters are usually smaller
- body size
- Larger breeds carry larger litters, roughly with weight to the 0.55 power
Worked example
With the default values below, Litter Size Predictor returns Expected Litter Size of 8.7. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Speciesone of Dog, Cat
- Dog
- Mother's adult weightminimum 0.5 kg
- 25 kg
- Mother's ageaccepts 0.5–15 years
- 3 years
- Previous littersminimum 0
- 1
Results
- Expected Litter Size
- 8.7
- Likely Range, Low
- 5
- Likely Range, High
- 14
- Age Adjustment
- 1.050 x
- Guidance
- A radiograph from around day 45 gives a far more accurate count than any prediction
Step by step
- 1Values used
- 2Litter Size Predictor
- 3Expected Litter Size= 8.7
- 4Likely Range, Low= 5
- 5Likely Range, High= 14
- 6Age Adjustment= 1.050 x
- 7Guidance= A radiograph from around day 45 gives a far more accurate count than any prediction
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
- This is a statistical estimate only. Breeding decisions carry health risks for the mother and offspring and should be made with veterinary advice. An accurate count requires imaging by a veterinarian.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
This is a statistical estimate only. Breeding decisions carry health risks for the mother and offspring and should be made with veterinary advice. An accurate count requires imaging by a veterinarian.
Frequently Asked Questions
How is Litter Size Predictor calculated?
Litter size scales with maternal body size, adjusted for age and parity Litter size correlates with maternal body size in dogs but is fairly constant in cats. First litters run smaller and size declines after about seven years of age.
Why does Litter Size Predictor matter?
A radiographic count near day 45 is the only reliable figure, and knowing it beforehand is what makes a retained fetus detectable during whelping.
What values do I need to enter?
This calculator takes 4 inputs: Species, Mother's adult weight, Mother's age, Previous litters. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.