Brownie Pan Conversion Calculator
8" sq vs. 9" sq vs. 9×13: scaling factor + bake-time delta. Same depth assumed.
Result
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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.
Frequently asked
Why double a recipe in a 9×13?+
Most boxed and standard brownie recipes are sized for 8" or 9" square. 9×13 has nearly 2× the area — needs full recipe doubling for proper depth.
Bake time can go up?+
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.
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