Chinese Hamsters may be small, but they are active, athletic animals that require more space than their tiny body size might suggest. The absolute minimum recommended floor space for a single Chinese Hamster is 450 square inches of unbroken floor area, though experienced keepers widely agree that 600 square inches or more leads to noticeably happier, healthier animals with fewer stress-related behaviors.
Floor space is more important than vertical height for hamsters, though Chinese Hamsters are uniquely skilled climbers among hamster species and will readily use vertical enrichment if provided safely. A long, wide enclosure with a moderate height gives you room for deep bedding, a wheel, hides, and climbing accessories without creating dangerous fall distances from elevated platforms.
Avoid the temptation to rely on tube systems and multi-level modular cages to compensate for limited floor space. While tubes provide some enrichment, they do not substitute for open running and foraging area. Many modular tube systems also have connection points that a slender Chinese Hamster can exploit to escape, as these hamsters are significantly thinner and more flexible than the Syrian Hamsters most commercial cages are designed for.
When evaluating cage dimensions, measure the interior floor space rather than the outer dimensions listed on the packaging. Thick plastic walls, base ramps, and built-in accessories can significantly reduce the usable floor area from what the box advertises.