Animal Gestation Calculator

What this calculator does

Find out when your animal is likely to give birth, starting from the date she was bred. Every species has its own typical pregnancy length (gestation). It runs from about a month in rabbits to around eleven months in horses. Knowing roughly when a birth is due lets you plan feed, housing, extra help and vet visits. That's true whether you keep a herd of cattle or a pair of guinea pigs. Each animal also has its own word for giving birth: cows calve, mares foal, goats kid, ewes lamb, sows farrow and rabbits kindle.

Choose the animal and enter the breeding date. The calculator adds the commonly quoted average pregnancy length to give an expected due date. It also shows the usual window of earliest and latest normal dates. And it tells you how far along the pregnancy is today, or on any date you pick. The figures are typical averages for planning. A veterinarian can confirm a pregnancy and give advice for your animal.

Where it's used

Why this math matters outside the classroom:

• Calving dates. Cattle farmers mark expected calving about 283 days after breeding to plan barn space and help.
• Foaling plans. Horse owners count about 340 days from breeding to plan for foaling and agree the timing with their vet.
• Small animals. Rabbit keepers count about 31 days from mating so a nest box is ready in time.
• Calendar math. Students practice adding days across month ends when they count 114 days forward for a pig.
• Youth livestock projects. Youth livestock clubs keep breeding and due dates in a record book alongside feed and weight logs.

How to use it

1. Choose the animal from the list.
2. Enter the breeding or insemination date. If there were several matings, use the first.
3. Leave the second date as today, or pick another date to see how far along she'll be then.
4. Read the expected due date, the usual window, and the days passed and still to go.

What the inputs mean

Animal

The averages are typical figures for each species. The real date can move by days because of the breed, the number of young, the season, feeding and the animal herself. In horses, it can move by weeks.

Breeding date

The date of mating or artificial insemination. Sometimes an animal is kept with a male for a while and the exact date isn't known. Then use the first possible date, and expect the birth later in the window.

Progress on this date

The date to measure progress on. It starts as today's date on your device. Dates are treated as calendar days, with no time zone conversion.

Formula and method

expected due date = breeding date + typical gestation (days)
usual window = breeding date + earliest days  to  breeding date + latest days
days since breeding = chosen date − breeding date
progress = days since breeding ÷ typical gestation × 100

Here are the typical pregnancy lengths used, counted from breeding: cow 283 days (usually 279–292), horse 340 days (320–370), goat 150 days (145–155), sheep 147 days (142–152), pig 114 days (111–117), rabbit 31 days (28–35), guinea pig 65 days (59–72) and cat 64 days (58–67). These are rounded averages of the kind given in livestock care (animal husbandry) references. They aren't exact limits.

The math is plain calendar counting. Whole days are added to the breeding date, so month ends, year ends and leap days are all counted correctly. Progress is the share of the typical length that has passed. It can go over 100% if the animal goes past the average date.

Worked example

A cow was bred on September 18, 2026. When is she due, and how far along is she on October 18, 2026?

1. Expected due date: Sep 18, 2026 + 283 days = Monday, Jun 28, 2027.
2. Usual window: day 279 is Thursday, Jun 24 and day 292 is Wednesday, Jul 7, 2027.
3. On Oct 18, 2026 she is 30 days past breeding.
4. Progress: 30 ÷ 283 × 100 = 10.6% of a typical pregnancy, with 253 days to go.

Result: The calf is expected around Monday, Jun 28, 2027, most likely between Jun 24 and Jul 7, 2027. On Oct 18, 2026 she is 30 days along.

Understanding the result

Think of the expected date as the middle of a range. Have housing, bedding and help ready from the start of the window, especially when you're not sure of the breeding date.

Contact a veterinarian promptly if an animal goes well past the latest usual date, shows signs of distress, or labor doesn't progress. A vet can also confirm pregnancy, often by ultrasound or a blood test, and advise on care late in pregnancy.

Not every breeding leads to a pregnancy. The calculator assumes a pregnancy and can't confirm one.

Assumptions and limitations

• Pregnancy is counted from the breeding date, using a typical average length for the species.
• The usual window is a commonly quoted range for normal births, not a strict limit.
• With several matings, the first date is the starting point.
• Breeds and individual animals vary. Some healthy births fall outside the window, especially in horses.
• The calculator gives dates only. It doesn't assess health, fertility or the number of young.
• Dogs have their own calculator, and species not listed here have different pregnancy lengths.

Frequently asked questions

How this calculator is checked

Method: Calendar arithmetic on the breeding date using commonly quoted average gestation lengths and usual ranges for each species (rounded husbandry reference figures). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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