Biology countdown

Animal gestation and incubation calculator

Estimate birth or hatch dates for 30 mammals and birds with cited species references.

Animal birth and hatch date calculator

Choose a species and enter a mating, breeding, or egg-laying date to estimate the typical due date and normal range.

SpeciesMating date

Predicted date

Mar 25, 2027

Countdown

280 days left

Normal range

Mar 11, 2027 to Apr 8, 2027

Human (Homo sapiens)

Typical period: 280 days
Group: mammal
Litter: 1 infant

Merck Manual: stages of pregnancy

Species	Days	Range	Litter or clutch	Sources
Bald eagle Haliaeetus leucocephalus	35	34-36 days	1-3 eggs	San Diego Zoo
Canada goose Branta canadensis	30	25-30 days	2-8 eggs	Cornell
Chicken Gallus gallus domesticus	21	20-21 days	1 egg per chick	Source
Emperor penguin Aptenodytes forsteri	64	62-67 days	1 egg	Smithsonian
Mallard duck Anas platyrhynchos	28	26-30 days	8-13 eggs	Cornell
Mute swan Cygnus olor	42	35-42 days	4-8 eggs	Cornell
Ostrich Struthio camelus	42	42-46 days	5-11 eggs	San Diego Zoo
Scarlet macaw Ara macao	28	24-28 days	2-4 eggs	San Diego Zoo
Turkey Meleagris gallopavo	28	26-28 days	10-14 eggs	Cornell
Asian elephant Elephas maximus	660	600-670 days	1 calf	Smithsonian Smithsonian
Blue whale Balaenoptera musculus	365	305-365 days	1 calf	San Diego Zoo NOAA
Cat Felis catus	65	63-65 days	3-5 kittens	Merck
Cow Bos taurus	283	279-287 days	1 calf	Merck
Dog Canis lupus familiaris	63	62-64 days	1-12 puppies	Merck
Giant panda Ailuropoda melanoleuca	135	95-160 days	1-2 cubs	Smithsonian
Giraffe Giraffa camelopardalis	453	420-468 days	1 calf	San Diego Zoo
Goat Capra hircus	150	145-155 days	1-3 kids	Merck
Golden hamster Mesocricetus auratus	16	15-18 days	6-8 pups	Source
Horse Equus caballus	340	320-360 days	1 foal	Merck AVMA
House mouse Mus musculus	19	19-21 days	5-10 pups	Source
Human Homo sapiens	280	266-294 days	1 infant	Merck
Lion Panthera leo	110	100-119 days	2-4 cubs	Smithsonian
Pig Sus scrofa domesticus	114	112-115 days	8-12 piglets	Merck
Rabbit Oryctolagus cuniculus	33	31-33 days	4-12 kits	Merck
Red fox Vulpes vulpes	52	49-58 days	4-6 kits	Smithsonian
Red kangaroo Osphranter rufus	36	33-38 days	1 joey	San Diego Zoo
Sheep Ovis aries	152	144-152 days	1-3 lambs	Merck
Tiger Panthera tigris	105	93-112 days	2-4 cubs	Smithsonian
Virginia opossum Didelphis virginiana	13	12-13 days	8-13 joeys	Smithsonian
Western lowland gorilla Gorilla gorilla gorilla	257	250-290 days	1 infant	Smithsonian

These dates are planning estimates from species references. Individual animals vary by breed, health, age, season, and veterinary factors.

How animal gestation differs from incubation

Mammals carry developing young inside the body, so their gestation period is counted from mating or conception to birth. Birds develop in eggs outside the parent, so the calculator treats the bird entries as incubation periods from laying to hatch. The date math is the same, but the biology is different: a cow, dog, cat, gorilla, whale, or elephant is pregnant; a chicken, duck, ostrich, swan, eagle, or penguin egg incubates.

Elephant pregnancies are famous because they run about 22 months. A large calf needs time to develop the brain, body size, coordination, and trunk control needed for a herd-moving newborn. Smithsonian material lists Asian elephant gestation near 21.5 to 22 months, which is why this calculator uses 660 days for the typical estimate.

Blue whales are included because the largest animal on Earth is a sea mammal with a roughly year-long pregnancy. The table also includes short marsupial and rodent periods: opossums can give birth in under two weeks, while mice and hamsters are measured in days rather than months.

Sources include Smithsonian National Zoo, San Diego Zoo Wildlife Alliance, veterinary references including Merck and AVMA Journals, NOAA, Cornell Lab of Ornithology, and per-row citations in the calculator.