A 4ft by 2 ft hutch is the MINIMUM size for 2 piggies.
If you can buy bigger that is much better for the welfare of an animal.
Guinea pigs also need floor time each day too to have a good run and play either indoors if it is too cold or wet outside, otherwise a big run outside on fine warm days.
The probem with hutches are that lots of manufactors make them 18inch wide so its worth bearing in mind when purchasing a hutch that the living space is actually 2 foot as it makes an enormous difference.
There are lots of 6ft hutches for sale, although not many of this size are sold in pet stores, goodness knows why, but they are not promoting good care the welbeing of any animal by selling such small flimsy hutches.