Can you use an 8 inch mattress on a loft bed?

Yes, technically you can use an 8-inch mattress on a loft bed, but on a high loft configuration it will meaningfully cut into your headroom above the sleeping platform and may leave clearance too tight for comfortable use.

Dnxao's high loft beds are built around a 4-to-6-inch mattress as the reference point. With a platform height of roughly 63 inches and an 8-inch mattress in an 8-foot ceiling room, your sitting headroom drops to about 25 inches — workable for a child lying down, but tight enough that most adults will feel cramped. An 8-inch mattress works with far less risk on a low loft bed, where the platform sits 40–47 inches off the floor and ceiling clearance isn't the binding constraint.

• Dnxao's recommended mattress thickness for high loft beds: 4–6 inches.
• Minimum ceiling height for Dnxao high loft beds: 8 feet absolute minimum, 8.5 feet recommended.
• Clearance formula: ceiling height minus platform height minus mattress thickness equals sitting headroom.
• With a 63-inch platform, 8-inch mattress, and 8-foot ceiling, sitting headroom is approximately 25 inches.
• Dnxao low loft bed platform height range: 40–47 inches — more forgiving with thicker mattresses.