Cake Pan Size Converter
Swap pans by volume, not guesswork — area ratio in, bake adjustments out.
Swap pans by volume, not guesswork — area ratio in, bake adjustments out.
The pan the recipe was written for
The pan you want to use
Pick both pans to get the volume ratio and the bake adjustment.
Common pan areas
| Pan | Bottom area |
|---|---|
| 6" round | 28.3 in² |
| 8" round | 50.3 in² |
| 9" round | 63.6 in² |
| 8" square | 64 in² |
| 9" square | 81 in² |
| 9 × 13 rectangle | 117 in² |
| Loaf 9 × 5 | 45 in² |
| Bundt 10" (10–12 cup) | 78.5 in² |
The ratio between pans does the work, not the absolute numbers. Bundt pans are sold by capacity instead of diameter.
Frequently asked questions
What is the volume difference between 8-inch and 9-inch round pans?
Area scales with the square of the diameter: an 8" round is 50.3 in² and a 9" round is 63.6 in², so the 9-inch holds 1.27× more batter at the same depth. Pour an 8-inch recipe into a 9-inch pan and the cake bakes about 27% thinner — expect it to finish roughly 15–25% sooner.
How do I convert a round pan to a square pan?
Match areas, not names. A 9" round (63.6 in²) and an 8" square (64 in²) are within 1% of each other — ratio 1.006 — so they swap one-for-one with no timing change. As a rule of thumb, a square pan holds about 27% more than the same nominal round (8" square = 64 in² vs 8" round = 50.3 in²).
How does pan size change baking time?
Through batter depth, not the pan's name. Target area under 0.8× the source means deeper batter: drop the oven 25°F and allow 25–50% more time. Over 1.25× means shallower: same temperature, 15–25% less time. In between, timing is close — start checking about 5 minutes early. The skewer, not the clock, has the final word.
Can I use a 9×13 instead of two 9-inch rounds?
Almost. Two 9" rounds total 127.2 in² against the 9×13's 117 in², so the sheet is 0.92× the volume — inside the 'similar' band. Bake at the recipe's temperature, expect the sheet done a few minutes before the rounds would have been, and cut squares instead of wedges.
How much does a Bundt pan hold?
The classic 10-inch Bundt is sold by capacity — about 10 cups, some stamped 10–12 — rather than by diameter, which is why it appears in capacity charts but not in pure area tables. Fill it only two-thirds to three-quarters full; the tall walls and center tube mean longer, slower baking than a flat layer cake.
How the conversion works
With the same batter height, the volume ratio equals the area ratio — so the whole conversion is two areas and one division.
1. Source area: π × (diameter ÷ 2)² for rounds, side × side for squares, length × width for rectangles. 2. Target area the same way. 3. Ratio = target ÷ source. 4. Read the guidance: below 0.8 bake deeper and longer; above 1.25 shallower and faster; otherwise treat it as a swap.
Worked example — recipe written for a 9×13, baked in a 9" round:
Areas: 117 in² vs 63.6 in². Ratio: 63.6 ÷ 117 = 0.544 — well under 0.8, so the round cake fills deeply: lower the oven 25°F, allow 25–50% more time, and test with a skewer before trusting the clock.
Why volume beats the name on the pan
Pan names hide area swings: '9-inch' covers 63.6 in² round but 81 in² square, and a 9×13 sheet is nearly two 9" rounds. Recipes written for one geometry under-fill or over-fill another — the ratio line is the honest comparison.
Metric pans convert the same way: a 24 cm round is 452 cm² and a 20 cm square is 400 cm² — ratio 1.13. The math is unit-blind as long as both pans share one system.
Guidance assumes the same batter height and oven type. Glass and dark pans brown faster — drop the temperature 25°F regardless of size.
Related Calculators
Explore more tools in the unit_converter category