The Differences Between Trundle & Twin Mattresses

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While both accommodate twin-size mattresses, a trundle bed has an additional twin-size stored underneath the top mattress.

Since the days of lumpy trundle bed, daybed and fold-away bed mattresses, the mattress industry has made technological advances. The twin-size mattress you buy as a standalone bed is not much different from the one you store in a rolling trundle unit. Both can offer a comfortable night's rest. But, there are some differences between trundle bed mattresses and standard twins.

Trundle by Definition

A trundle bed has two mattresses. The main unit is a twin-size mattress nestled in a frame which consists of three pieces: two side panels and one back panel. If the day bed has a trundle drawer or rolling steel frame with wheels, it will be stored in the space beneath the daybed. Unlike a standard twin mattress which requires a box spring and a steel frame for support, the trundle bed mattress rests on a platform or supporting slats. For smaller rooms, the ability to store an extra bed for occasional use frees up precious floor space.

Mattress Size

A standard twin-size mattress measures 39 by 75 inches. Extra long or California-long twin mattresses add an additional 9 inches, measuring 39 by 84 inches in length. Because of the trundle-bed frame, the length of the twin-size mattress is limited by the frame and the trundle unit. A pop-up trundle unit may accommodate a standard twin mattress; but, it's not uncommon to find 71-inch mattresses sized for trundle drawers.


Twin-size mattresses range in thickness from 6 to 18 inches, based on construction, quality and pillow-top features. Many trundle beds accommodate an 8-inch-thick twin mattress. But, it's not uncommon to find trundle mattresses that measure just 5 inches.


With technological advances in the mattress industry, materials used to construct trundle mattresses mean greater comfort. It also means less differentiation between a trundle mattress and a standard twin. Twin-size mattresses for freestanding beds and trundle units are manufactured from a wide range of materials. High-tech, antimicrobial memory foam, latex foam, pillow-top beds and air-chamber mattresses are just some of the alternatives available for use in trundle beds.

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Merle Huerta

Merle Huerta, an adjunct instructor of English skills, began writing during her husband's combat deployment to Iraq in 2003. Her articles have appeared in "The Jerusalem Post," and USA Travel Tips, among other publications. Huerta has an M.A. in instructional media and technology from Columbia University and is a graduate of CUNY's The Writers Institute.