Pan Size Converter

How it works

The converter computes the inside area of each pan shape — circle for round and bundt, square for square, rectangle for rectangular and loaf — and returns the ratio of target area to original area. That ratio is your ingredient scale factor: a target pan with 1.5x the area takes 1.5x the batter.

Bake time scales more gently than volume. Shallower batter (a bigger pan) finishes faster than the math would suggest; deeper batter (a smaller pan) needs more time. The tool gives a rough minute estimate and a temperature hint — about 25°F lower for a thinner layer, about 25°F higher if you're concentrating batter into a smaller pan.

Worked example

Converting a 9-inch round cake (about 63.6 sq in) to an 11-inch round (about 95 sq in) gives a 1.5x scale factor. Multiply every ingredient by 1.5, drop the oven temperature 25°F, and start checking the cake about 80% of the way through the original bake time. A 9-inch round to a 9x13-inch rectangular pan is a different ratio (117 sq in / 63.6 = 1.84x) and follows the same logic.

Common mistakes

Don't use the pan's outer dimensions — use the inside cooking area, which is what holds batter. Don't assume two "9-inch" pans from different brands hold the same batter; some run a quarter-inch larger and that matters at scale.

Don't use the converter to swap loaf pans for round cake pans at 1:1. Loaf pans are deep and narrow; round cakes are shallow and wide. The batter-to-surface ratio is fundamentally different and the bake profile will not match the original recipe's intent.

FAQ

Why doesn't the tool handle volume in cups? Because pan capacity is an unreliable proxy for what you actually care about (batter depth). Two pans can hold the same cups of batter but bake very differently if one is shallow and one is deep. Surface area is the right primitive.

What about bundt and tube pans? Bundt pans bake like ring-shaped cakes with more crust-to-interior ratio. Tube (angel food) pans are even taller and narrower; halve the scale factor mentally before applying — they're already designed to bake large volumes in a small footprint.

How accurate is the bake time hint? Good to within about 10% for round and rectangular pans. Loaf, bundt, and tube pans are more variable — always start checking earlier than the tool suggests.