What are the dimensions of a KING mattress? A standard Australian king mattress is 183 cm wide and 203 cm long. It's the same length as a queen mattress but has an extra 30cm in width. Perfect if you want to stretch out or need some extra room for the kids. All our king mattresses are Australia made by the award-winning Comfort Sleep Bedding and we only use environmentally friendly ingredients: GECA approved foams and natural fabrics. Plus, all of our mattresses are covered by a 10-year guarantee, so you can be sure you’re investing in a quality mattress that will stand the test of time. So, if you’re looking for your perfect king size mattress visit our Sydney showroom in Rozelle.