Care guide · Mice

Pet mouse cage size: how big it really needs to be

Checked against Wood Green: Caring for mice as pets, PDSA: The ideal home for your mice, MSD Veterinary Manual: Providing a home for mice and 5 more on

A cage for three or four pet mice should be at least 80 × 50 × 35 cm (31 × 20 × 14 in), and 100 × 50 × 35 cm (39 × 20 × 14 in) for up to six, as Wood Green recommends. Bars must be no more than 6 mm (¼ in) apart, the floor solid, and the cage well aired. Most pet shop mouse cages are smaller than this.

How big should a mouse cage be?

As big as you can fit, starting from 80 × 50 cm (31 × 20 in) of floor. Mice look tiny, but the RSPCA notes wild mice can travel many hundreds of metres in a day, and pet mice still need room to run, climb, dig and forage. The cage also has to hold a 20 cm (8 in) wheel, at least two hides, a dig box and food spread around, and still leave open floor.

Number of mice Size we'd use Floor area
2 or 3 80 × 50 × 35 cm (31 × 20 × 14 in) 4,000 cm² (620 sq in)
4 80 × 50 × 35 cm (31 × 20 × 14 in) 4,000 cm² (620 sq in)
5 or 6 100 × 50 × 35 cm (39 × 20 × 14 in) 5,000 cm² (775 sq in)
7 or 8 120 × 50 × 35 cm (47 × 20 × 14 in) 6,000 cm² (930 sq in)

The first three rows are Wood Green's sizes. Wood Green gives nothing smaller than 80 × 50 cm, so we use that for a pair too. The last row is our own step up from Wood Green's numbers, not a charity figure.

What is the minimum cage size for mice?

The smallest figure from a vet source is 45 × 45 × 25 cm (18 × 18 × 10 in) for two or three mice, from the MSD Veterinary Manual. Sources vary a lot, so here they are side by side.

Source Size For
PetMD 51 × 25 × 30 cm (20 × 10 × 12 in), "bigger is better" 1 mouse
MSD Veterinary Manual 45 × 45 × 25 cm (18 × 18 × 10 in) 2 or 3 mice
Wood Green 80 × 50 × 35 cm (31 × 20 × 14 in) 3 or 4 mice
Wood Green 100 × 50 × 35 cm (39 × 20 × 14 in) up to 6 mice
PDSA, RSPCA No figure; "plenty of space" any group

We follow Wood Green. It is the only source that sizes the cage to the group, and its numbers leave room for everything the RSPCA and PDSA say mice need inside. PetMD's figure is for a lone mouse, and UK charities say mice should never live alone.

What is the minimum cage size for 3 mice?

For three mice, use at least 80 × 50 × 35 cm (31 × 20 × 14 in). Three females is a common, steady group, and Wood Green gives this size for three or four. The MSD manual's 45 × 45 × 25 cm (18 × 18 × 10 in) is a floor area about half that, and in our view it only works as a short-term or hospital cage.

How tall should a mouse cage be?

About 35 cm (14 in) is enough. That is the height in Wood Green's sizes, and it fits an upright wheel plus one or two low shelves. Mice are good climbers, and the RSPCA says shelves and climbing frames make the cage more interesting and help them move about with confidence.

Height is less useful than floor, though. The RSPCA warns mice can break limbs falling or jumping from height inside the cage, and RSPCA Australia asks for levels and climbing surfaces that prevent falls. In a tall cage, add shelves every 15 cm (6 in) or so and hang ropes and hammocks between them, so no mouse can drop the whole height. That spacing is our suggestion, based on keeping every possible fall short.

What bar spacing does a mouse cage need?

No more than 6 mm (¼ in). The PDSA and PetMD both give this figure. Wood Green allows 7 to 9 mm (about ⅓ in) but calls 7 mm the safest, and young mice in particular can slip through gaps that look far too small. We'd take the PDSA's 6 mm.

Rabbit, guinea pig and many rat cages have bars far wider than 6 mm. However big and cheap they are, a mouse will be through the bars in seconds. Measure the gap with a ruler before you buy.

What makes a good large mouse cage?

A good large mouse cage has a deep solid base, narrow bars, a big door and good airflow. Size alone is not enough.

Cage type Good Watch out for
Barred cage on a deep plastic base Best airflow, things clip to the bars, easy to clean Bar spacing over 6 mm; shallow base that spills bedding
Glass tank with mesh lid Holds deep bedding, no mess PDSA advises against; PetMD says solid walls trap ammonia
Wooden cage or vivarium Looks nice MSD manual calls wood unacceptable: urine soaks in and builds ammonia
Wire-floored cage None for mice Hurts feet and legs (MSD, RSPCA Australia)

For extra-large setups, look for a cage with a base at least 15 cm (6 in) deep, so you can pile bedding high enough to burrow. That depth is our suggestion: the RSPCA asks for bedding deep enough to burrow in, and a shallow tray cannot hold it. Our best pet mouse cages page lists ones that pass these tests.

Mouse cage size calculator: a simple rule

Give three or four mice 4,000 cm² (620 sq in) of floor, then add about 500 cm² (78 sq in) for each extra mouse. That rule comes from the step between Wood Green's two sizes. Never go below 80 × 50 cm for any group, and keep the height around 35 cm (14 in).

  1. Count your mice. Plan for the group you have, not the group you hope to keep small.
  2. Work out the floor. 4,000 cm² (620 sq in) for up to four, plus 500 cm² (78 sq in) per extra mouse.
  3. Check the shape. Long and wide beats tall and narrow. A 50 cm (20 in) depth fits a wheel and hides side by side.
  4. Check the bars. 6 mm (¼ in) or less, everywhere, including the door.
  5. Check the floor. Solid, with a base deep enough to hold bedding.

What needs to fit inside the cage?

The size only works if everything below still leaves open floor. Use this list to check a cage before you buy it, then follow our mouse cage setup guide to lay it out.

  • A solid, upright wheel of 20 cm (8 in), as Wood Green recommends
  • At least two hides with more than one exit each
  • A dig box of coco coir or plain organic compost
  • One or two low shelves or levels
  • Ropes, tubes and branches to climb
  • Deep bedding across the whole floor; see our mouse bedding guide
  • A water bottle and a spot for scattering food

Before buying, draw the cage floor on paper at full size and set out a dinner plate for the wheel and two mugs for the hides. If there is little paper left showing, the cage is too small.

A bigger cage also helps keep the peace. The RSPCA says hides and tubes with several exits let mice avoid trouble with cage mates. If you are planning a group, see male or female mice, and for the whole picture, our pet mouse care guide.

Mouse cage size questions

Is a 45 x 45 cm cage big enough for mice?

It is the bare minimum the MSD Veterinary Manual gives for two or three mice, at 45 x 45 x 25 cm (18 x 18 x 10 in). Once a 20 cm wheel, two hides and a dig box go in, there is little floor left to run on. We'd treat it as a travel or hospital cage, not a home.

Can mice live in a glass tank?

UK charities advise against it. The PDSA says to avoid glass and plastic cages, and PetMD notes solid walls trap ammonia from urine. If you use a tank, it needs a full mesh lid, deep bedding changed often and a cool, airy room. A barred cage with 6 mm bars is the safer choice.

Is a hamster cage OK for mice?

Only if it passes the same tests: at least 80 x 50 cm (31 x 20 in) of floor for three or four mice, bars no more than 6 mm (1/4 in) apart, a solid floor and good airflow. Many hamster cages are too small or have bars wide enough for a mouse to slip through.

Do mice need a tall cage?

They need some height but floor space matters more. Wood Green's sizes are 35 cm (14 in) high, which fits a wheel and one or two low levels. Very tall cages add fall risk, and the RSPCA warns mice can break limbs falling from height, so keep levels low and add ropes and hammocks.

What is a mouse cage size calculator?

A simple rule to scale the cage to your group. Working from Wood Green's sizes, give three or four mice 4,000 square cm (620 square in) of floor and add about 500 square cm (78 square in) for each extra mouse. Never go below 80 x 50 cm for any group.

Does a bigger cage make mice fight less?

Room to get away helps. The RSPCA says hides and tubes with several exits let mice avoid confrontations with cage mates, and those need space. A cramped cage gives a bullied mouse nowhere to go. Space alone will not fix a badly matched group of adult males, though.

Sources

Read next

Pet mouse care: the complete guide

Keep mice in same-sex groups in a big barred cage with deep paper bedding, hides, a solid wheel, about 5 g of mouse nuggets each a day and daily spot cleans.

Pet mouse cage setup: layouts and ideas that work

A good mouse cage has deep paper bedding, two-exit hides, a solid 20 cm (8 in) wheel, low levels, climbing ropes, a dig box and scattered food.

Best pet mouse cages: what to buy and what to skip

The best mouse cage is barred, at least 80 x 50 x 35 cm (31 x 20 x 14 in), with bars 6 to 7 mm (1/4 in) apart and a deep, solid base for bedding.

Best bedding for pet mice: what is safe and what to avoid

Dust-free, unscented paper or card bedding is best for pet mice, with plain tissue or hay to nest in. Avoid sawdust, cedar, pine, scented types and cotton wool.

Male or female mice: groups, pairs and living alone

For most people, a group of three or more female mice is easiest. Males often fight once grown and smell stronger; a neutered male can live with females.