How Long Do Mice Live? Mouse Lifespan Calculator

General information only. Lifespans are averages from veterinary and research sources; your mouse may live longer or shorter. For health worries, see an exotic-animal vet. We give no medication or dosing advice.

How long do mice live?

How long do mice live? It depends almost entirely on where the mouse lives. A pet mouse usually lives 1.5–2.5 years (Merck Veterinary Manual), a house mouse in the wild usually 9–12 months (UC IPM), and lab mice of the most-used strain have a median lifespan of about 29–30 months (Jackson Laboratory). All three are the same species, the house mouse, Mus musculus; the difference is safety, food and warmth.

So how long does a mouse live for in general? Plan on about two years for a pet and under a year for a wild mouse. The questions "how long do mouse live" and "how long does a mice live" have the same answer, and the average lifespan of a mouse kept as a pet is about 2 years — the middle of Merck's range and the average the calculator uses.

Mouse lifespan at a glance

• Pet / fancy mouse: 1.5–2.5 years (Merck); Merck's professional table gives 1–2 years.
• House mouse (wild): usually 9–12 months, some up to 3 years (UC IPM); most don't pass 12–18 months (Animal Diversity Web).
• Deer mouse and field mouse: usually under a year in the wild, but up to 8.3 years in captivity for a deer mouse (AnAge).
• Lab mouse: median about 894–901 days for C57BL/6J (Jackson Laboratory / Mouse Phenome Database).
• Oldest mouse ever: Patrick Stewart, a Pacific pocket mouse, at 9 years 209 days (Guinness, 2023).

How long do mice live as pets?

How long do mice live as pets? Usually 1.5–2.5 years. That's the Merck Veterinary Manual's "usual life span" for pet mice, and the pet mouse lifespan this calculator uses. Merck's table of pet rodent biology is a little lower, at 1–2 years, which reflects how many pets die young from illness.

The fancy mouse lifespan is the same: fancy mice are pet house mice bred for colour, coat and temperament. Merck notes that adults weigh 20–40 g, and males are usually a little larger than females. The calculator's "My pet mouse" mode shows how much of a typical lifespan your mouse has used, the average months left and its life stage.

How long do mice live in captivity?

In captivity generally — pets, zoos and labs — house mice usually live about 2 years (Animal Diversity Web), and the AnAge database gives 4 years as the longest reliably recorded for the species, set by a male from a wild-derived lab strain. Mutant and calorie-restricted lab mice can live longer, but those aren't normal pets. The longest-lived pet house mouse in Guinness records was Fritzy, who reached 7 years 225 days in the UK (1977–1985).

Male vs female mouse lifespan

We found no source that gives pet male and female mice different lifespans, so the calculator treats them the same. Lab studies find differences that depend on the strain, which doesn't translate into a rule for pets. What does differ is behaviour: female mice usually live peacefully in groups, while adult males often fight, so ask an exotic vet or rescue before housing males together.

How long do house mice live indoors and in the wild?

How long do house mouse live when they move into a building? UC IPM, the University of California's pest management programme, says the house mouse lifespan is "usually 9 to 12 months", although some have lived up to 3 years. Cornell's IPM programme adds that house mice can spend their entire lives indoors, getting enough moisture from food.

So how long do mice live in house walls, lofts and kitchens? Typically under a year. Indoor mice escape the weather and many predators, but they still face cats, traps and disease, and we found no study that measures indoor and outdoor house mice separately. Outdoors, the Animal Diversity Web says most wild house mice don't live beyond 12–18 months.

How long do mice live in the wild?

The wild mouse lifespan is short for every common species. Owls, hawks, cats, foxes, weasels and snakes all hunt mice (Animal Diversity Web), and cold, wet weather and food shortages kill many young mice. That's why the mice you see outdoors are mostly young: few survive to a second winter.

Field mouse, deer mouse and lab mouse lifespan

"Mouse" covers many species. The table compares the ones people ask about most; the calculator's "Mouse type comparison" mode shows the same figures with a bar chart against the pet rat.

• Field mouse lifespan: in Europe "field mouse" usually means the wood mouse, or long-tailed field mouse (Apodemus sylvaticus). The Animal Diversity Web gives about 1 year in the wild and up to 4–4.4 years in captivity.
• Deer mouse lifespan: North America's deer mouse (Peromyscus maniculatus) usually lives less than a year in the wild but up to 8 years in captivity (Animal Diversity Web; AnAge 8.3). Deer mice can carry hantavirus, so never handle wild ones.
• Lab mouse lifespan: C57BL/6J mice have a median lifespan of about 894–901 days (29–30 months), and medians across studies range from 600 to 980 days (Jackson Laboratory / Mouse Phenome Database).

Oldest mouse ever

Guinness World Records lists the oldest mouse ever as Patrick Stewart, a Pacific pocket mouse born at San Diego Zoo Safari Park in 2013, aged 9 years 209–210 days in February 2023. Pocket mice belong to a different rodent family from house mice, though. The previous record holder, and the oldest pet house mouse in the record books, was Fritzy, at 7 years 225 days.

Lifespan of mice and rats compared

People often search for the lifespan of mice and rats together, or the lifespan of rats and mice, because the two are easy to confuse. Rats live a little longer:

Mouse vs rat lifespan: why rats live longer

The mouse vs rat lifespan gap follows the usual rule that smaller mammals with faster metabolisms live shorter lives. Per gram of body weight, an adult mouse eats about 12 g of food per 100 g a day against about 5 g for a rat (Wayne State University IACUC) — well over twice the rate. Researchers who line up rodent and human lives also find mice ageing faster: averaged over a whole life, about 9 mouse days match one human year (Dutta & Sengupta 2016), against about 13.8 rat days (Sengupta 2013). Both species are weaned at about three weeks and reach puberty at about six, but a rat's adult years stretch out further.

Do rats live longer than mice? Yes, on average by about six months to a year as pets: 2–3 years for a rat against 1.5–2.5 for a mouse. Rats are also about ten times heavier. For the full picture on rats, see our pet rat lifespan calculator; for wild species, the wild rat lifespan guide.

Why mice have such short lives

Small mammals with fast metabolisms tend to live short lives, and mice are a textbook case. A mouse eats about a tenth of its body weight every day (ICWDM), and its life runs on fast-forward: weaned at 3–4 weeks, sexually mature at about 6 weeks (AnAge), and able to have 5–10 litters a year (Animal Diversity Web).

The Jackson Laboratory, which breeds lab mice, describes mouse maturation as about 150 times faster than a human's in the first month, about 45 times faster for the next five months and about 25 times faster after 6 months. Researchers Dutta and Sengupta (2016) estimate that, over a whole life, about nine mouse days equal one human year. In the wild, that fast life is cut shorter still by predators, cold and hunger, so most wild mice never reach old age at all.

What do pet mice usually die of?

We found no study of causes of death in pet mice. In lab mice, the AnAge database notes that cancer is the main cause of death across most populations, though the details vary a lot from strain to strain. For a pet, that means lumps, weight loss, a hunched posture or noisy breathing all deserve a prompt visit to an exotic-animal vet — small rodents hide illness well, and a mouse can go downhill in days. Respiratory problems are worth extra care because ammonia from dirty bedding irritates the airways of all small rodents, so regular cleaning is one of the simplest things you can do.

Mouse life stages

Signs your mouse is getting old and how to care for it

The Jackson Laboratory classes lab mice as middle-aged at about 10–14 months and old at 18–24 months. Common signs of an old mouse include:

• sleeping more and running on the wheel less;
• a thinner, rougher or greasy coat, because grooming slows;
• weight loss and a more bony back;
• a hunched posture or stiffer movement;
• lumps under the skin, or changes in breathing.

Some of these also mean illness, so see an exotic-animal vet rather than assuming it's age. Here's how to help a pet mouse live longer — the basics are simple:

• Feed a complete rodent pellet and check food and water every day — mice eat and drink a lot for their size.
• Keep the cage clean and roomy, with a solid wheel, hides and nesting material, and low ammonia.
• Give suitable company: usually a group of females; adult males often fight.
• Weigh weekly and see an exotic vet about lumps, wheezing or weight loss.
• For seniors, lower climbing heights, add soft nesting and keep food and water within easy reach.

How this mouse lifespan calculator works

My pet mouse uses Merck's typical 1.5–2.5 year range and its middle, 2 years. A 6-month-old mouse has used 25% of that average, a 1-year-old 50% with about 12 months left on average, and an 18-month-old 75%. Mice past 2.5 years see a "true senior" message, and ages past the 7 years 225 days pet record show an error. The life stage follows weaning (Merck), sexual maturity (AnAge) and the Jackson Laboratory's age bands. Sex and the care checklist don't change the numbers, because no source puts a figure on them; they add notes and tips.

Mouse type comparison shows the typical and longest-known lifespan for five kinds of mouse, why they differ, and bars against the pet rat for scale. If your pet has stopped eating or drinking, see our guide to how long a mouse can live without food — and call a vet.

Frequently asked questions

This calculator gives an estimate for education and fun. Every pet ages differently — for health decisions, talk to your veterinarian.