Pan size conversion

When a recipe calls for a pan you do not own, the key is to keep the depth of the batter or dough about the same. The University of Nebraska-Lincoln Extension suggests using an 8x8 or 9-inch round pan when halving a recipe written for a 9x13 pan, and an 8x5-inch loaf pan when halving a recipe written for an 8x8 or 9-inch round.

It also says that when glass replaces metal, the oven temperature should drop by 25 degrees F. A smaller or deeper pan changes how fast heat reaches the center, so bakers start checking for doneness early and rely on cues such as a golden top and a clean toothpick.

For exact conversions, bakers compute each pan's volume: length times width times height for a rectangle, and pi times the radius squared times the height for a round pan. Dividing one volume by the other gives a scaling factor for the recipe.