BakeSpan / Guide
How to measure a baking pan
The number on a label is a starting point. The inside of your actual pan is what the calculation needs.
Measure the inside, not the handles
For a straight-sided round pan, measure across the inside of the pan through its center. That measurement is the diameter, not the radius. Do not include the thickness of the wall, a rolled rim, or handles. For a rectangle, record the inside width and inside length.
Keep the original unit visible. An 8-inch pan and a 20-centimeter pan are close in size, but they are not identical: 8 inches is 20.32 centimeters. BakeSpan accepts an independent unit for each pan, so you can compare them without treating rounded labels as exact equivalents.
Equal depth means equal batter depth
The simple area ratio assumes the batter sits at the same depth before baking. It does not mean filling both pans to the brim. The space a recipe needs to rise remains a separate practical constraint. Check the recipe and your actual pan before using a new size.
When this model is the wrong tool
A tapered loaf pan can have different dimensions at the base and rim. A Bundt pan has a central tube and a shaped interior. These are not plain cylinders or boxes. A pair of width measurements cannot describe their usable capacity reliably, so this release does not calculate them.
A measured-capacity comparison can be a different approach, but it needs a consistent measurement method and intended fill level. It is not implemented here. Do not substitute the outside dimensions to force a result from the simple tool.
A quick pre-calculation check
- Both pans are round or rectangular with straight sides.
- You have the inside measurements and their actual units.
- The number of pans is correct on both sides.
- The recipe allows the intended fill level and room to rise.
- You are comparing equal batter depth, not inventing a new baking time.
Further reading: Calculation method, sources, and limitations. These examples are arithmetic explanations, not tested recipes.