Height is the dimension chinchillas actually use
Most small pets live on the floor of their cage; a chinchilla lives in the whole volume of hers. Wild chinchillas are rock-hoppers, and a pet chinchilla crosses her cage in leaps between shelves, ricocheting off walls and ledges at speeds that make floor area almost a secondary measurement. So size the cage vertically: around a metre wide, sixty centimetres deep and a metre or more tall is a sound home for a pair, and taller is genuinely better if the room allows it. A wide, low cage of the same volume frustrates the animal it houses, because her natural way of moving has nowhere to go.
Single chinchillas — usually kept as pairs, but sometimes alone for welfare reasons — need the same tall footprint. Solitude is not a reason to shrink the cage; if anything, the leaping circuit is a bigger part of a lone chinchilla's day.
Fill the height with shelves, not empty air
A tall empty box is not the same as a tall home. Fit solid shelves — kiln-dried pine, or metal — at staggered heights and depths so the cage becomes a climbing route with landings, and so a chinchilla who misjudges a leap falls one short level onto a shelf rather than the full height onto the floor. A clear drop of more than about half a metre is a broken-leg risk for an animal built light and fast, so break every long drop with an intermediate ledge.
Keep the shelves solid rather than mesh. Chinchilla feet are bare-soled and built for rock; standing life on wire grids hurts them, and a leg slipped between bars in a midnight leap can fracture. The cage floor itself should be solid or covered — many metal cages come with a pull-out tray under a grid, and covering that grid with a fleece liner, tiles or a solid pan is a standard early improvement.
Bars, spacing and the chewing audit
Everything within tooth reach will be chewed, so the cage structure itself must be metal: plastic bases, plastic shelf clips and wooden cage frames all eventually open under chinchilla teeth, and an escapee built like a spring is nobody's idea of a quiet night. Bar spacing should be no more than about two centimetres in any direction — chinchillas compress surprisingly well, and youngsters or smaller adults can work through gaps that look modest. Check door catches with the same suspicion: they should be positive latches, because a chinchilla will test a spring catch with her teeth until it learns to open.
Wheels, if you add one, must be large — a small wheel bends a chinchilla's spine backwards as she runs — solid-surfaced, and mounted so the leaping route does not pass through it. Many keepers skip wheels entirely and let the shelves do the work.
Placement counts as part of the size
A chinchilla's cage belongs in a cool room — these are animals in fur coats designed for mountain nights, and a cage that fits perfectly but stands over a radiator or in a sun-trap window is the wrong home in the right dimensions. Place the cage where daytime temperatures stay comfortably low, out of direct sun and away from draughts at floor level, with the understanding that the room's evening activity is welcome: chinchillas are crepuscular and enjoy a household winding down around them.
Measure the gap the cage must pass through before it arrives — a metre-tall assembled cage does not fold, and more than one has been built in the wrong room. Writing the final measurements, shelf layout and bar spacing on your chinchilla's KinsLe profile through Family Sharing means the next purchase in the family — a spare shelf, a holiday cage, a replacement door — gets checked against the numbers that fit her, instead of arriving as a guess.