Siman 634
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א סֻכָּה שֶׁאֵין בָּהּ שִׁבְעָה עַל שִׁבְעָה, פְּסוּלָה; וּלְעִנְיַן גֹּדֶל, אֵין לָהּ שִׁעוּר לְמַעְלָה.
1 A Sukkah Must Not Be Less Than 7 x 7, containing 4 Seifim: A sukkah that is not at least 7 x 7 is invalid. Regarding the maximum, there is not a measurement above.
ב אִם הִיא עֲגֻלָּה, צָרִיךְ שֶׁיְּהֵא בָּהּ כְּדֵי לְרַבֵּעַ שִׁבְעָה עַל שִׁבְעָה.
2 If it is circular, it must contain within 1/4 circle, a measure of 7 x 7.
ג יֵשׁ בָּהּ שִׁבְעָה עַל שִׁבְעָה, וְנָתַן בָּהּ בְּגָדִים לְנָאוֹתָהּ וּמְמַעֲטִים אוֹתָהּ מִשִּׁבְעָה עַל שִׁבְעָה, פְּסוּלָה.
3 If the sukkah is 7 x 7 and one places fitting garments in it and it reduces the size below the minimum, it is invalid.
ד מִי שֶׁהָיָה רֹאשׁוֹ וְרֻבּוֹ בַּסֻכָּה, וְשֻׁלְחָנוֹ חוּץ לַסֻכָּה וְאָכַל, כְּאִלּוּ לֹא אָכַל בַּסֻכָּה, אֲפִלּוּ אִם הִיא סֻכָּה גְּדוֹלָה, גְּזֵרָה שֶׁמָּא יִמָּשֵׁךְ אַחַר שֻׁלְחָנוֹ.
4 One whos head and most of his body is inside the sukkah, and his table is outside the sukkah and he eats as if it he cannot eat in the sukkah - even if it is a large sukkah, there is a gezeirah (against this) on case he might be pulled after his table.