Nominal mattress size
The market label and reference dimensions used to identify a family, such as US Queen or UK King. It is not a guarantee for every product.
Compare the finished mattress with the frame’s internal opening.
The exterior footprint is for room planning. It does not tell you whether the mattress will sit correctly inside the frame or base.
Finished mattress
The physical width, length and depth of the specific mattress, including its finished cover and the manufacturer’s allowed variation.
Frame internal opening
The usable area intended to receive and support the mattress, bounded by rails, lips, upholstery, corners or mechanisms.
Frame exterior footprint
The overall furniture dimensions, including headboard, rails and posts. Use this for room and access planning, not mattress fit.
Bedding dimensions
Fitted sheets and protectors depend on mattress depth as well as width and length; a matching market name alone is insufficient.
Why a close match is not a guarantee
Soft edges, seams, rounded corners, assembly variation and retaining rails can change the practical relationship. BedMetric provides no universal allowance: verify both manufacturers’ current dimensions and instructions.
Next practical steps
Use the complete mattress and frame checklist · Compare named sizes at true scale · Resolve the country naming first