Pan Size Conversion Calculator
Scale a recipe when changing baking pan sizes.
For round pans, enter the diameter in both fields
Results update as you type.
How it works
When you want to bake a recipe in a different pan than it calls for, you need to scale the ingredients to match the new pan's area, and this calculator finds the factor. You enter the original pan's dimensions and the new pan's dimensions, and it returns the scaling factor to multiply your ingredients by, along with the percentage change. The principle is that batter should sit at roughly the same depth in the new pan as in the original, so the recipe scales with the pans' surface areas, not their linear dimensions. The calculator divides the new pan's area by the original's; multiply every ingredient by this factor to fill the new pan to a similar depth. For rectangular pans, enter length and width directly. For round pans, enter the diameter in both fields, which works because the ratio of the diameters squared equals the ratio of the circular areas, giving the correct factor. So moving from a 9-inch square to a 9-by-13 pan gives a factor of about 1.44, meaning you increase the recipe by roughly 44 percent. Remember that baking times may change too: a shallower or wider pan often bakes faster, so check for doneness earlier. Enter your original and new pan dimensions to compute the scaling factor.
Scale = new pan area / original pan area
The scaling factor is the area of the new pan divided by the area of the original pan. Multiplying each recipe ingredient by this factor keeps the batter depth, and thus the bake, similar. For round pans, entering the diameter in both dimension fields makes the ratio of the squared diameters equal the ratio of the areas.
Source:Baking reference
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter original pan length, original pan width, new pan length and new pan width.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Scaling factor updates instantly as you type — no button to press.
Frequently asked questions
How do I convert a recipe to a different pan size?
Divide the new pan's area by the original pan's area to get a scaling factor, then multiply every ingredient by it. Moving from a 9-inch square to a 9-by-13 pan gives a factor of about 1.44. The calculator computes this from your pan dimensions so you can scale the recipe correctly.
Why scale by area instead of dimensions?
Batter fills a pan's floor and rises to a depth, so the amount needed depends on the pan's surface area, not its length or width alone. Scaling by area keeps the batter depth similar, which keeps baking behavior consistent. Scaling by a single dimension would give the wrong amount and change how the item bakes.
How do I handle round pans?
For a round pan, enter its diameter in both the length and width fields. This works because multiplying the diameter by itself is proportional to the circular area, so the ratio of the two pans' entries equals the ratio of their true areas. The scaling factor then comes out correct for round-to-round conversions.
Do baking times change with pan size?
Often yes. A wider or shallower pan spreads batter thinner and usually bakes faster, while a deeper pan bakes slower. After scaling the ingredients, start checking for doneness earlier or later than the original time, and use visual and toothpick tests rather than relying solely on the recipe's stated time.
Can I scale to any pan?
You can scale between most pans, but extreme changes may affect results: a much deeper batter can bake unevenly, and a very thin layer can dry out or overbake. Modest changes work best. For big differences, consider adjusting temperature or splitting the batter, and always watch the bake rather than trusting the original timing.