Baking Pan Size Conversion Calculator
You have a recipe written for one pan but only own another. Enter the shape and dimensions of the pan the recipe calls for and the pan you want to use, and this calculator works out the floor area of each and the ratio between them. That ratio tells you how much to scale the batter — because capacity follows area, not the diameter or the side length. It is a starting point for a confident substitution, not a guarantee that every recipe transfers cleanly.
Original pan (what the recipe calls for)
Target pan (what you want to bake in)
Scale the batter by
1.84×
Bigger pan — use about 184% of the original batter.
Original area
63.62 in²
Target area
117.00 in²
Conversion detail
Keep the oven temperature the same. A shallower, wider pan bakes a little faster and a deeper, narrower pan a little slower, so check for doneness early and do not fill any pan more than about two-thirds full.
Pan area comparison
How it works
The calculator finds the floor area of each pan. A round pan's area is π × (diameter ÷ 2)², and a rectangular or square pan's area is length × width. Area is the honest measure of how much batter a pan holds at a given depth, which is why a 9-inch round pan (about 63.6 in²) and a 9×13 pan (117 in²) are so different even though the numbers look similar at a glance.
It then divides the target pan's area by the original pan's area to get the scaling ratio. A ratio above 1 means the new pan is bigger, so multiply the recipe's batter — including a proportional amount of leavening, sugar, and liquid — by that factor. A ratio below 1 means the new pan is smaller, so scale down and expect leftover batter if you use the full recipe. Multiplying by area, not by diameter, is the key: doubling a pan's width more than doubles its capacity.
Finally it reports the ratio as a percentage of the original recipe so you can eyeball the adjustment. Keep the oven temperature the same and adjust bake time instead: a shallower, wider pan bakes faster, while a deeper, narrower pan bakes slower, so start checking for doneness a few minutes earlier or later and rely on a toothpick or thermometer rather than the clock.
Frequently asked questions
Why scale by area instead of pan diameter?+
Because capacity grows with area, and area grows with the square of the diameter. A round pan's area is π × (radius)², so going from an 8-inch to a 10-inch round pan is not a 25% increase — it is 100 ÷ 64 of the area, about a 56% increase in the batter it holds at the same depth. If you scaled by diameter you would badly under-fill the larger pan. Comparing floor areas gives the ratio that actually matters for how thick the batter sits.
Do I need to change the oven temperature or bake time?+
Keep the temperature the same and adjust the time. Batter depth is what changes when you swap pans: a wider, shallower layer bakes faster and a deeper, narrower one bakes slower. As a rule of thumb, start checking a shallower pan several minutes before the original time and give a deeper pan extra time, then judge doneness by a clean toothpick, a springy top, or an internal temperature rather than by the recipe's stated minutes.
Can I always just fill the new pan with the scaled batter?+
Not blindly — do not overfill. Most cakes and quick breads want the pan roughly half to two-thirds full so they have room to rise without spilling or sinking. If the ratio tells you to increase the batter but your pan is shallow, split the batter across two pans or bake in batches. Very delicate items like soufflés, angel food, and some layer cakes depend on pan geometry in ways a simple area ratio cannot capture, so treat those conversions cautiously.