Guinea pigs need flat running space, not tall cages with levels. In the wild they run, popcorn, and chase across open ground, and a cage that gives them room to sprint in a straight line keeps them fitter and calmer than any multi level tower. This free cage size calculator turns your herd size into a minimum floor area in square metres and square feet, plus an example rectangle shape, so you can check a cage before you buy it.
The minimum sizes come from welfare guidance used by rescues and vets. One guinea pig needs at least nought point seven square metres, two pigs need at least one square metre, and each extra pig adds about nought point three square metres. These are minimums, not targets: bigger is always better, and a cage at the minimum will feel small once hides, hay racks, and tunnels go in.
Using the calculator takes seconds. Enter how many guinea pigs you have and press Calculate cage size. The result shows the minimum floor area, the same area in square feet for shoppers using imperial sizes, an example rectangle with a nought point seven metre width, and the herd size you entered. Compare the result with the inside floor size of any cage you consider, not the outside size printed on the box.
A worked example shows the pattern. Two pigs need one square metre, which is about ten point eight square feet, and an example shape of about one point four three metres by nought point seven metres. Three pigs need one point three square metres, four pigs need one point six, and five pigs need one point nine. The jump per pig is small on paper but obvious in the cage, since each pig needs its own hide and feeding space.
Levels and ramps do not count towards the minimum, and that surprises many buyers. Guinea pigs have fragile backs and poor depth perception, so steep ramps cause falls and injuries, and most pigs avoid upper levels anyway. A flat cage with a loft for sleeping can be a bonus, but the ground floor alone must meet the minimum area. If a shop advertises total area across two levels, check the ground floor size before you trust the number.
Bigger cages pay back in behaviour and health. Pigs in roomy cages popcorn more, squabble less, and use separate toilet corners, which keeps the rest of the cage cleaner. Small cages push pigs into each other, and that friction causes chasing, barbering, and even bites in boars. If two pigs that got along suddenly fight, lack of space is one of the first causes to check, before blaming character.
Building your own cage is often cheaper than buying one, and C and C cages made from grids and correx are the classic choice. A two by four grid cage suits two pigs, a two by five suits three, and bigger herds need longer runs. Whatever you build, measure the inside floor, keep the walls at least thirty centimetres high, and place the cage in a draught free room at a steady temperature away from direct sun.
Floor time outside the cage does not replace cage size, and that distinction matters. An hour of free roaming helps, but pigs spend most of the day in the cage, and a small cage still means cramped nights, crowded feeding, and nowhere to escape a cage mate. Think of floor time as a bonus on top of a proper cage, not as a fix for a small one. If space at home is tight, a cage that meets the minimum plus daily floor time beats a tiny cage with long floor time, because the cage is where pigs sleep, eat, and toilet for most of their lives. Measure first, buy once, and give the pigs the room they will use every hour of every day.