Mattress sizes vary to accommodate different sleeping needs and preferences. The most common sizes include Twin, Full, Queen, and King. A Twin mattress measures 38 inches by 75 inches, making it ideal for children or single sleepers. A Queen mattress, measuring 60 inches by 80 inches, is popular among couples for its spaciousness. King mattresses are the largest, measuring 76 inches by 80 inches, providing ample space for two people. Full mattresses, at 54 inches by 75 inches, offer a bit more room than a Twin but are still suitable for smaller bedrooms. Choosing the right size ensures comfort and restful sleep.