What are the dimensions of a single mattress? A single mattress measures 92 cm x 187 cm, the smallest mattress of all Australian standard sizes. The single mattress and bed are the perfect size for one person. Ideal for kids, a spare room or any room you may need a smaller mattress. Looking for another size? See our King single, Double, Queen and King size mattresses. We only use GECA approved foams and natural ingredients in our single mattresses.