Abstract: A convertible bed frame assembly is configured to support a mattress. The bed frame assembly incorporates first and second side-by-side rectangular bed platforms. Each bed platform has a horizontal support surface, opposing lateral ends, and opposing interior and exterior longitudinal sides. A removable center extension is configured to reside between the interior longitudinal sides of the side-by-side bed platforms and coplanar with respective horizontal support surfaces. When installed, the center extension functions to separate the side-by-side bed platforms thereby increasing the width of the bed frame assembly. When removed, the side-by-side bed platforms combine together to reduce the width of the bed frame assembly.