A King size mattress will measure approxmately 76 x 80.
It varies, which is why mattress pads and fitted sheets state that they fit a range of depths.
Never heard of a Texas King mattress a California King is 6 inches longer than a standard king
Twin 38" x 75" Full/Double/Regular 53" x 75" Queen 60' x 80" King 76" x 80" Cal. King 72" x 84"
its 60W X 80L (in inches)