Cake Pan Size Converter
Convert any cake recipe to a different pan size and get an adjusted baking time instantly. Use this when substituting a 9-inch round for a 8-inch square or any other pan swap.
Last updated: September 2026
Formula below · 2 sources (fdc.nal.usda.gov, Wikipedia) · Updated Sep 2026
Compare with similar
About this calculator
When the same batter goes into a pan of a different size, its depth changes in inverse proportion to the pan's area, and bake time depends mainly on batter depth because heat must reach the center of the layer. Round-pan area scales with diameter squared, so: newBakeTime ≈ originalBakeTime × (originalDiameter / newDiameter)². A smaller pan holds the batter deeper and needs longer; a larger pan spreads it thinner and needs less time. Treat this as a starting point — bake time does not grow exactly in proportion to depth — and start checking about 10 minutes early. The pan-depth fields do not change the time; use them to check that the new pan is deep enough (the batter should fill it no more than about two-thirds). For pans more than about 3 inches deep, lower the oven by 25°F and use a heating core or flower nail so the edges do not overbake before the center sets.
How to use
Suppose your recipe calls for a 9-inch round with a 35-minute bake, and you want to use an 8-inch round. newBakeTime = 35 × (9/8)² = 35 × 1.266 ≈ 44.3 minutes, because the same batter sits about 27% deeper in the smaller pan. Start checking around 35 minutes with a toothpick. Going the other way, from an 8-inch to a 9-inch pan, the time drops to 35 × (8/9)² ≈ 27.65 minutes.
Frequently asked questions
How do I convert a 9x13 inch pan recipe to two 9-inch round pans?
A 9×13 pan has an area of 117 square inches, while two 9-inch rounds together offer about 127 square inches. The volumes are close enough that you can use roughly the same bake time, but start checking 5 minutes earlier since the batter will be slightly shallower. Watch for the edges pulling away from the pan and use the toothpick test to confirm doneness. Baking temperature remains unchanged.
Why does changing pan size affect baking time so much?
Heat transfers from the outside of the batter inward, so the distance from the pan wall to the center of the batter determines how long baking takes. A larger pan spreads batter into a thinner layer, shortening the path heat must travel and reducing bake time. Conversely, a smaller or deeper pan increases that distance, requiring more time. For the same amount of batter, depth (and so time) scales roughly with the inverse square of the diameter ratio.
Should I change the oven temperature when using a different pan size?
In most cases you keep the same temperature, but there are exceptions. For very deep pans or dense batters, reducing the temperature by 25°F (about 15°C) helps the center cook through without the exterior over-browning. For very shallow pans or thin layers like sheet cakes, the original temperature is usually fine but bake time drops significantly. Always monitor visually and use a toothpick or cake tester rather than relying on time alone.