The 9x9" square pan has a base of 81 sq in (523 cm²).
The 9x9" square pan in centimeters, and pans of about the same size
Measured across the top, the 9x9" square pan is 22.9 × 22.9 cm, with a base of 523 cm².
Pans within 10 % of its area: one 10" round pan (78.5 sq in) or one 7x11" pan (77 sq in). A recipe for the 9x9" square pan fits these without scaling; if the batter ends up deeper or shallower, adjust the baking time.
Measure a pan across the top, from inside edge to inside edge, not across the bottom or the outside: that is the size recipes and labels give. Pans with sloped sides are smaller at the bottom than the size on the label.
Factors keep the batter as deep as in the 9x9" square pan. Below 1 means make less; above 1, more.
Frequently asked questions
How big is the 9x9" square pan?
Its base is 81 sq in (523 cm²).
How do I convert a recipe from the 9x9" square pan to the 9x13" pan?
Multiply the recipe by 1.44 (about 1 1/2 ×) so the batter stays as deep. The 9x13" pan is 117 sq in.
Does the baking time change?
If the batter is deeper or shallower than the recipe’s, yes: shallower bakes faster, deeper slower. Start checking early and use the recipe’s doneness test.