A little help in the kitchen
Baking pan size converter
Changing pans? Compare the base areas of the two pans to find how much to scale the recipe so the batter keeps the same depth.
Common baking pans
| Pan | Area (cm²) | Area (in²) |
|---|---|---|
| 8-inch round | 324.3 | 50.3 |
| 9-inch round | 410.4 | 63.6 |
| 8-inch square | 412.9 | 64.0 |
| 9-inch square | 522.6 | 81.0 |
| 9 × 13-inch rectangle | 754.8 | 117.0 |
| 20 cm round | 314.2 | 48.7 |
| 23 cm round | 415.5 | 64.4 |
| 20 cm square | 400.0 | 62.0 |
| 23 cm square | 529.0 | 82.0 |
| 23 × 33 cm rectangle | 759.0 | 117.6 |
Each area is calculated from the pan’s nominal size in its own unit (1 inch = 2.54 cm).
Why area matters
A cake or tray bake is designed for a certain depth of batter, and depth controls how fast the centre cooks. If the new pan has the same base area as the old one, the batter sits at the same depth and bakes in about the same time at the same temperature (Joy of Baking). So the calculator compares base areas and gives you one factor: multiply every ingredient by it and the batter keeps its depth in the new pan.
Pan area formulas
- Round pan: area = π × (diameter ÷ 2)²
- Square pan: area = side × side
- Rectangular pan: area = width × length
- Scaling factor = new pan area ÷ original pan area
- Change (%) = (factor − 1) × 100
Worked example: 20 cm round to 20 cm square
The round pan has an area of π × 10² = 314.2 cm². The square pan has 20 × 20 = 400 cm². The factor is 400 ÷ 314.2 = 1.27, so the square pan needs 27% more batter: 200 g of flour becomes 255 g, and every other ingredient rises by the same factor. Going the other way, from square to round, the factor is 0.79. A square pan always has 4 ÷ π, or about 1.27 times, the area of a round pan of the same width, whatever the size. Some swaps need no scaling: a 9-inch round (63.6 in²) and an 8-inch square (64 in²) are within 1% of each other.
Inches and centimetres
One inch is exactly 2.54 cm, so one square inch is exactly 6.4516 cm² (NIST). Area in cm² = area in in² × 6.4516. Pans sold in inches and centimetres are close but rarely identical:
| Inch pan | Inch pan area | Nearest metric pan | Metric pan area |
|---|---|---|---|
| 8-inch round | 324.3 cm² | 20 cm round | 314.2 cm² |
| 9-inch round | 410.4 cm² | 23 cm round | 415.5 cm² |
| 8-inch square | 412.9 cm² | 20 cm square | 400.0 cm² |
| 9-inch square | 522.6 cm² | 23 cm square | 529.0 cm² |
| 9 × 13-inch | 754.8 cm² | 23 × 33 cm | 759.0 cm² |
Differences of 1–3% rarely matter, but enter what your pan actually measures. Measure across the inside, from inside edge to inside edge (Crafty Baking).
Depth and volume caveats
- The factor keeps batter depth the same; it does not check that your new pan’s sides are tall enough. If you pour the original quantity into a smaller pan instead of scaling, the batter will be deeper and may overflow.
- Pans with sloping sides are wider at the rim than the base, and square pans with rounded corners hold a little less than side × side. Measure the same way for both pans so the comparison stays fair.
- Ingredients that come in units, such as eggs, rarely scale to whole numbers. Beat the eggs and weigh them so you can use the exact scaled amount.
Bake time, temperature and doneness
Scaling by area keeps the depth, so bake time usually stays close to the recipe, but check early: pan colour matters too, and King Arthur Baking finds light-coloured pans gentler on cake batter. When depth changes, time changes with it. King Arthur Baking bakes the same vanilla cake batter at 350 °F (177 °C) in three ways:
| Pans | Total area | Batter depth vs 9 × 13 | Bake time |
|---|---|---|---|
| One 9 × 13-inch | 117 in² (755 cm²) | 100% | 35–40 min |
| Two 9-inch rounds | 127 in² (821 cm²) | 92% | 30–35 min |
| Three 8-inch rounds | 151 in² (973 cm²) | 78% | 24–27 min |
Joy of Baking suggests a slightly shorter time and slightly higher temperature for shallower batter, and a longer time at a slightly lower temperature for deeper batter so the top does not over-brown. Judge doneness by the cake, not the clock: King Arthur Baking’s cake is ready when it is golden at the edges, just beginning to pull away from the pan, and a toothpick inserted in the centre comes out clean.
Pans the calculator does not cover
Bundt, tube, loaf and shaped pans have no simple base area, so compare volume instead. Fill each pan with water to measure its capacity (King Arthur Baking), then scale by new pan volume ÷ original pan volume (Joy of Baking). For a Bundt, King Arthur Baking measures usable capacity with water 1¼–1½ inches (3–4 cm) below the rim, keeps the batter at least 1¼ inches below the rim, and notes that the roughly 6 cups (1.4 litres) of batter for a 9 × 13-inch or two 9-inch rounds suits a 10-cup (2.4 litre) Bundt pan, baked about 30% longer than the recipe says. Joy of Baking lists an 8½ × 4½ × 2½-inch loaf pan at 6 cups (1.4 litres) and a 9 × 5 × 3-inch loaf pan at 8 cups (1.9 litres).
Scaling in CookBook
In CookBook’s cooking mode you can change a saved recipe’s servings and its ingredient amounts scale with them, so multiplying the servings by the pan factor scales the whole recipe (8 servings × 1.27 is about 10). Cooking time does not scale, so check doneness yourself.
Sources
A little more help
Frequently asked questions
Can I bake an 8-inch square recipe in a 9-inch round pan?
Yes. An 8-inch square pan has an area of 64 square inches and a 9-inch round pan 63.6 square inches, less than 1% apart, so you can use the recipe as written.
How do I convert a 9 × 13-inch recipe to two 8-inch round pans?
Two 8-inch rounds have about 100.5 square inches in total against 117 for the 9 × 13-inch pan, so multiply the ingredients by about 0.86. Two 9-inch rounds (127 square inches) are close enough to take the full recipe, as King Arthur Baking’s vanilla cake shows.
Should I change the oven temperature when I change pans?
Usually not if you scale the recipe by area, because the batter depth stays the same. If the batter ends up noticeably deeper or shallower, adjust the time first, and only change the temperature slightly.
Can I use the calculator for cupcakes?
No, it compares single pans. As a guide, King Arthur Baking’s vanilla cake batter for one 9 × 13-inch pan also makes 24 cupcakes, baked for 23 to 25 minutes instead of 35 to 40.
Why does the calculator compare area instead of volume?
Most cakes and bars are poured to a set depth rather than filling the pan, so matching the base area keeps the depth, and with it the bake time, close to the original. Volume is the better guide for Bundt, tube and loaf pans.
Still have a question? Visit our help centre.
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“Baking pan size converter”, CookBook Manager. Updated . https://cookbookmanager.com/tools/baking-pan-converter
Text, tables and data on this page are available under the Creative Commons Attribution 4.0 licence (CC BY 4.0). Credit CookBook Manager and link to this page when you reuse them.
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