Rockstar has not released any official map size for Grand Theft Auto VI, so there is no confirmed answer to how much bigger it will be than GTA V. The game is set in the state of Leonida, which includes Vice City and surrounding areas, but no dimensions or square kilometre figures have been provided. Any specific numbers you see online are community estimates, not facts.
What is known: GTA V’s map, set in Los Santos and Blaine County, was approximately 49 square kilometres, a figure Rockstar did confirm at the time. For GTA VI, the only confirmed details are the setting and the two protagonists, Lucia and Jason. Reports and leaks have suggested a larger map, possibly including multiple cities or a more expansive rural area, but these remain unconfirmed. Rockstar has not commented on map size, mission count, or how it compares to previous titles.
For now, treat any size comparison as speculation. The map page on this site will be updated if Rockstar releases official details. Until then, the best reference is the in-game world shown in the trailers and the extended look, which give a visual sense of scale but no measurable data. If map size matters to you, wait for official confirmation before drawing conclusions.