How big should a rat cage be?
The common rule used by rat clubs and rescues is 2 cubic feet of cage per rat, with a floor of at least about 2 × 1.5 ft and enough height for climbing. Rats are active climbers, so a tall cage with several levels, hammocks and ropes gives them far more usable space than a low one of the same volume.
Number of rats = volume ÷ 2, rounded down
Worked example
A cage 36 in long, 24 in wide and 38 in tall: 36 × 24 × 38 ÷ 1,728 = 19 cubic feet, enough for 9 rats by volume. Most owners keep fewer than the maximum so there is room for toys and hides.
Common rat cage sizes
| Cage (L × W × H) | Volume | Rats by the 2 cu ft rule |
|---|---|---|
| 24 × 14 × 16 in (small store cage) | 3.1 cu ft | 1 (too small for a pair) |
| 30 × 18 × 30 in | 9.4 cu ft | 4 |
| 36 × 24 × 24 in (single level) | 12 cu ft | 6 |
| 36 × 24 × 38 in | 19 cu ft | 9 |
| 36 × 24 × 63 in (double unit) | 31.5 cu ft | 15 |
Other things to check
- Bar spacing: ½ inch or less for adult males; ⅜ inch for females and young rats, which can squeeze through ½ inch gaps.
- Floor: solid floors and shelves, or cover wire with fabric or tiles. Wire floors hurt feet and cause bumblefoot.
- No glass tanks: they trap ammonia from urine and harm rats' sensitive lungs.
- Company: keep at least two rats of the same sex. Single rats get lonely and stressed.
- Free-range time: at least an hour a day outside the cage in a safe area.
Other small pets? The small pet cage size calculator covers guinea pigs, rabbits, hamsters, gerbils, ferrets and chinchillas. See how old your rat is with the pet age calculator.
Sources: rat club and rescue cage guidelines (2 cubic feet per rat, bar spacing); RSPCA rat care guidance.
Frequently asked questions
How many rats can live in my cage?
Multiply length, width and height in inches, divide by 1,728 to get cubic feet, then divide by 2. A 36 × 24 × 38 in cage is 19 cubic feet, enough for 9 rats.
How big a cage do 2 rats need?
At least 4 cubic feet, but bigger is better. A cage about 30 × 18 × 30 in (9 cubic feet) gives a pair plenty of room to climb.
What bar spacing is safe for rats?
Half an inch or less for adult males, and ⅜ inch for females and young rats.
Can rats live in a fish tank?
It is not recommended. Tanks have poor airflow, so ammonia builds up and can cause breathing problems, which rats are prone to.
Should rats live alone?
No. Rats are very social and should live with at least one other rat of the same sex.
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Last updated October 2026.