Hamster cage size
Let's start off with this question.
Why are small cages bad?
Firstly, you can't fit enough enrichment in them. They simply cannot provide a happy life for a hamster. They cause a lot of stress and boredom- some boredom behaviours (which are commonly seen as 'normal hamster behaviour') include- wall scaling, climbing the bars and bar-biting. The majority of small cages don't allow enough bedding to be added for burrowing.
Minimum-
The least or smallest amount or quantity possible, attainable, or required.
The size 450squ inches of floorspace is often viewed as enough for hamsters- but where did that information come from? It came from a hamster forum called The Hamster Hideout where they decided on the minimum in 2015. There was no scientific research or evidence behind this decision. This was just based on the fact that the largest Ikea Samla bin cage was that size. And before that, the minimum was 360squ inches, based on the US 20 gallon long tank. Again, this was not based on any scientific research.
In 2007, an article was published which showed how the cage size affected the behaviour of hamsters. 60 female Syrians were housed individually in 4 different cage sizes- 279squ inches, 387squ inches, 775squ inches and 1550squ inches. Although bar biting was observed in all cage sizes, there was a significant amount of bar biting in the smaller cages compared to the larger cages. The Veterinary Association for Animal Welfare says 'The golden hamsters, which are active at night and require a lot of exercise, need the largest possible housing system with the minimum dimensions of 100 cm x 50 cm x 50 cm'. The Blue Cross say 'The ideal home for a hamster is housing no smaller than 100cm x 50cm floor space'. The PDSA and Hamster Welfare.com also recommends 100 x 50cm as a minimum.
So from this we know we should be aiming for above 775squ inches of floorspace (100 x 50cm). Here are some cages that you can buy/diy that are suitable for hamsters: IKEA Pax, IKEA Platsa, IKEA Linmon, The 115 X 60CM Pawhut and the hexagonal Pawhut, Large glass tanks, most Niteangel cages, Living world eco habitat, Rodipet Nagarium
Image above- The 115cm X 60cm Pawhut enclosure
Image above- A fully DIY enclosure 100cm x 61cm
Image above- A fully DIY enclosure 120 x 75cm (mesh was added to the lid after the photo was taken)
Image above- The IKEA Platsa 180cm x 80cm
Image above- The IKEA Pax 201 x 75cm
A minimum isn't something to aim for. The minimum is there because anything under that is seen as unethical. You should always aim for above the minimum.
Personally, I recommend 1000squ inches of floorspace for all species of hamsters except for Syrians where I recommend 1550squ inches of floorspace, due to their size and the fact that they are usually not happy in a cage that's 775squ inches.