Most are full or queen size.

Standard twin mattress is 39" x 75"
Standard twin mattress is 54" x 75"
Model A Length B Height C Depth
chair
D Depth
Bed
Weight
DHP (Full) 80.5 37 39.5 53 101
Marin (Full) 79.4 34.1 35.3 54
Gel Memory Foam (Full) ?
Mainstays (full) 77 34 35 52.5
Twin
DHP (twin) 71 32 34 43 81
Model A Width B Height C Depth
chair
D Length
Bed
Weight
Cotton Cloud (twin) 39 37.5 75.5
Brayden (twin) 40.2 31.5 32.5 72.4 65
Millard (twin) 38 14 29 78 15
Olee (twin) 38 12 26 78 10
Full Size $287 DHP Bergen Wood Arm Futon with 6-inch Coil Mattress| Amazon $344 Marin Futon Dark Cherry Set | The Futon Shop
$208 Full-size Gel Memory Foam Futon Mattress - Overstock.com $129 Mainstays Silver Metal Arm Futon Frame with Full Size Mattress | Walmart
Twins Standard twin mattress is 39" x 75" $150-$189 depending on upholstery DHP Emily Convertible Futon | Walmart $320 Brayden Studio | Wayfair $600 - $880 Cotton Cloud Frame: Autum $460 Fuji $360 You need to get 2 mattresses for this configuration. 28" x 54" for the chair $120 - $285 28" x 21" for the built-in ottoman. $80 - $170 Cotton $165 Lovejoy $455 Alberta $200 Cover $40 - $365 The built-in ottoman only works in the bed position. You can get a free standing ottoman base for the extra mattress when the other is used as a chair. Full Size Mattress Construction: $200 All Cotton Lovejoy Mattresses are 10-12" thick when new but will compress some. Covers from $40- $365 are separate See other covers below. Size Guide $260 Austin Au Natural 8-inch Loft All Cotton Futon Sofa Sleeper Bed - Sit N Sleep : Target $180 WOW The SOFA BED, LOUNGE CHAIR | Amazon $100 Millard Tri-Fold Foam Folding Mattress and Sofa 4.5" Olee trifold $55 Olee Sleep Tri-Folding Memory Foam Mattress, Blue, 4"
Links:
Fitted Mattress covers for Twin, Full and Queen mattress sizes $55 twin
5 Best Futons | Best Reviews
Twin futons | Futon Planet
Murphy Beds for Sale in the USA - Online Wall Bed Shop | Multimobeds.com

last updated 1 Dec 2017