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Cake Pan Calculator / 8x8 square to 9x13 pan
King Arthur & Joy of Baking Geometry Standard

8x8 Square Pan to 9x13 Pan — Doubling Brownie & Bar Recipes

Area-based volume scaling for round, square, loaf, Bundt, and 9x13 sheet pans.

Scaling Ratio
1.83x (Nearly Double the Batter)
A 9x13 pan has 117 sq in vs 64 sq in. Double the recipe (2x) and bake for roughly the same time.
Never fill pans more than 2/3 full
Interactive Pan Area Comparator

Pan Geometry & Oven Science Guide

An 8x8 square pan has an area of 64 sq inches. A 9x13 rectangular pan has an area of 117 sq inches. The 9x13 pan is 1.83x larger (almost exactly double).

This is the most common conversion for doubling brownie, blondie, or bar recipes. Double the recipe (2x) and pour into a 9x13 pan; the bars will be slightly thicker and bake in 30–35 minutes.

Standard Cake Pan Surface Area & Volume Guide

Surface area dictates batter depth, while volume dictates maximum safe capacity.

Pan Name & Dimensions Surface Area Batter Capacity Ratio vs 8" Round
6-inch Round (2" deep) 28 sq in 4 cups 0.56x
8-inch Round (2" deep) 50 sq in 6 cups 1.00x (baseline)
9-inch Round (2" deep) 64 sq in 8 cups 1.27x
10-inch Round (2" deep) 79 sq in 10-11 cups 1.57x
8x8-inch Square (2" deep) 64 sq in 8 cups 1.27x (matches 9" round)
9x9-inch Square (2" deep) 81 sq in 10 cups 1.61x
9x13-inch Rectangle 117 sq in 14-15 cups 2.33x (matches two 9" rounds)
8.5x4.5-inch Loaf Pan 38 sq in 6 cups 0.76x
9x5-inch Loaf Pan 45 sq in 8 cups 0.90x
10-inch Bundt Pan 78 sq in 12 cups 1.55x
9-inch Springform Pan 64 sq in 10 cups (3" deep) 1.27x

Pan Substitution Rules & Baking Physics

Doubling Rule

Double the 8x8 recipe (2x) to fill a 9x13 pan with rich, thick brownies.

Exact Ratio

A 9x13 pan is 1.83x the area of an 8x8 square (117 sq in vs 64 sq in).

Bake Time for Brownies

A doubled 9x13 brownie batch bakes in roughly the same time (30–35 min at 350°F) as an 8x8 batch.

Frequently Asked Questions

How do I convert an 8x8 brownie recipe to a 9x13 pan? +
Double the ingredients (2x). An 8x8 pan is 64 sq in, while a 9x13 is 117 sq in (1.83x larger).
Do doubled brownies in a 9x13 pan bake longer than in an 8x8? +
They bake in roughly the same time (usually 2 to 5 minutes longer), because the batter depth remains relatively constant.
Can I bake a single 8x8 recipe in a 9x13 pan? +
Not recommended; the batter will spread paper-thin, baking dry and crispy within 15 minutes.

Related Pan Conversions

8 inch to 9 inch cake pan →9 inch to 8 inch cake pan →9x13 pan to round pan →9x13 pan to 8 inch round →9x13 pan to 9 inch round →8 inch round to 8 inch square →9 inch round to 8 inch square →9 inch round to 9 inch square →8 inch round to 9 inch square →9x9 square to 9x13 pan →8 inch round to loaf pan →9 inch round to loaf pan →10 inch bundt to 9x13 pan →10 inch bundt to round pan →6 inch to 8 inch cake pan →8 inch to 10 inch cake pan →
Baking & Kitchen Cluster Cross-Links

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