If you scale up but use a thicker pan or more depth, yes. The approximation here assumes equal depth.

Edge vs. center brownies?

Big pans = more edge. If you love edges, use 9×13. If you love middles, use 8" square (more center per recipe).

Does the metal/glass matter?

Glass holds heat, runs ~25°F warmer at the food. Drop temp by 25°F or take out 5 min sooner.

Why not a depth-based formula?

For most home brownies, depth is similar (1-2"). When depth changes a lot, switch to volume-based.

Brownie Pan Conversion Calculator

8" sq vs. 9" sq vs. 9×13: scaling factor + bake-time delta. Same depth assumed.

Result

Recipe scaling factor

1.83×

New bake time ~18 min (vs. 32 original).

Original pan8sq (64 in²)
New pan913 (117 in²)
Area ratio1.828×
Recipe scale× 1.828 on all ingredients
Original bake32 min
New bake (est)18 min
Bake delta-14 min

Step-by-step

From area = 64 in², To area = 117 in².
Ratio = 117 / 64 = 1.828.
Scale recipe ingredients by 1.828.
Bake time inversely scales: 32 / 1.828 ≈ 18 min.

How to use this calculator

Pick original pan from recipe.
Pick the pan you have.
Multiply recipe ingredients by the ratio.
Adjust bake time and check early with toothpick.

About this calculator

Brownies are area-driven: a 9×13 pan has 1.83× the area of an 8" square, so the recipe needs to be multiplied by 1.83 — or the pan-half-filled. If you keep the original recipe in a bigger pan, batter thickness drops, sides over-bake, and edges turn to leather. The bake-time scaling is approximate: a thinner sheet bakes faster (less thermal mass to heat through), but only slightly. Always check with a toothpick at 70% of estimated time.