Cake Pan Conversion Guide: Resize Any Recipe Without Guessing
Converting a recipe from an 8-inch round to a 9x13 without the math is how you end up with a dense, overbaked brick. Here is the formula, the chart, and a calculator.
Your recipe calls for an 8-inch round and you only have a 9×13. Can you swap them? Yes — but not at the same temperature, not for the same time, and not without adjusting the batter quantity. This guide gives you the volume math, a full conversion chart, and the bake-time adjustments that prevent a sunken middle.
The one rule that makes pan conversion work
Match the volume of batter to the volume of the pan. Diameter alone doesn't cut it — a 9-inch round 2 inches deep holds about 8 cups, while a 9-inch round 3 inches deep holds 12. Same diameter, 50% more capacity.
Once you know the volume your recipe was written for and the volume of the pan you want to use, the conversion is straightforward division.
Pan volume chart (working volume, fill to 2/3)
| Pan | Working volume |
|---|---|
| 6 in round × 2 in deep | 4 cups |
| 7 in round × 2 in deep | 5.5 cups |
| 8 in round × 2 in deep | 6 cups |
| 9 in round × 2 in deep | 8 cups |
| 10 in round × 2 in deep | 11 cups |
| 12 in round × 2 in deep | 15 cups |
| 8 in square × 2 in deep | 8 cups |
| 9 in square × 2 in deep | 10 cups |
| 9×13 in × 2 in deep | 14 cups |
| Standard loaf (9×5) | 6 cups |
| Bundt (10 in) | 12 cups |
| Standard cupcake well | 0.25 cups |
Pick the original pan and the new pan — get scaled batter quantities and adjusted bake times instantly.
Common substitutions and what they require
8-inch round → 9-inch round
Volume ratio: 8 ÷ 6 = 1.33. The new pan holds 33% more, so your original recipe will bake thinner. Reduce bake time by ~5 minutes and check at 75% of the original time. Same temperature.
9-inch round → 8-inch square
Both pans hold 8 cups — a near-perfect swap. Bake at the same temperature and time; check 5 minutes early because square corners cook faster than round edges.
8-inch round → 9×13 pan
9×13 holds 14 cups vs 6 — more than double. You'll need to multiply the recipe by 2.3× for a similar layer thickness, or accept a thinner sheet cake (which bakes 25–35% faster).
9×13 → two 8-inch rounds
Two 8-inch rounds = 12 cups vs the 9×13's 14 cups. Use ~85% of the original recipe and split between the two pans. Reduce bake time by 30–40% (rounds bake faster because they have more surface area per cup).
Bundt → two loaf pans
A 10-inch bundt (12 cups) splits cleanly into two standard 9×5 loaf pans (6 cups each). Bake at the bundt's temperature minus 25°F (15°C) and check at 75% of the bundt's time.
Bake time and temperature adjustments
| Change | Temperature | Bake time |
|---|---|---|
| Larger / shallower pan | −25°F (−15°C) | Reduce 20–30% |
| Smaller / deeper pan | −25°F (−15°C) | Increase 20–35% |
| Same volume, different shape | No change | Check 5 min early |
| Glass instead of metal | −25°F (−15°C) | Same as metal |
| Dark non-stick metal | −25°F (−15°C) | Reduce 5 min |
| Cupcakes from a layer recipe | Same | Reduce by 50%+ |
Pan shape conversion specifics
Round to square
A square pan holds about 25% more batter than a round pan of the same edge length / diameter. For an 8-inch round → 8-inch square swap, increase the recipe by 25% or accept a thinner cake (and reduce time by 5–8 minutes).
Round to rectangle (sheet pan)
Sheet cakes bake faster because the batter is shallow. A two-layer round recipe baked as a 9×13 sheet typically needs 25–35% less time at the same temperature.
Round to bundt
Bundt pans hold more batter and have more surface area thanks to the centre tube. Reduce temperature by 25°F (15°C) to prevent over-browning and bake 10–15 minutes longer than the equivalent round.
Special-case conversions
Cupcakes from a cake recipe
Each standard cupcake well holds 0.25 cups. A two-layer 8-inch recipe (12 cups of batter) yields 24 cupcakes filled 2/3, or 18 filled 3/4. Bake at the same temperature but reduce time by 50–60% — standard cupcakes are done in 18–22 minutes.
Mini cakes from a single recipe
A 4-inch round mini cake holds about 1.75 cups. Each 8-inch recipe yields 6–7 minis. Reduce bake time by ~40%.
Tiered cake from a single recipe
For a 4 + 6 + 8 inch tiered cake, you need approximately 2 + 4 + 6 = 12 cups of batter. A standard layer cake recipe (12 cups) covers the entire tiered cake — a useful rule when scaling up.
What you cannot easily convert
Some pans don't play well with substitutions:
- Angel food and chiffon recipes — these need the tube pan's structure to rise. Don't convert.
- Cheesecake — the springform's straight sides matter for unmoulding. Use a different size springform, not a different pan type.
- Soufflés — the ramekin's height-to-width ratio is essential to the rise.
Frequently Asked Questions
Can I use a 9-inch pan instead of an 8-inch pan?+
Yes. A 9-inch round holds about 33% more batter than an 8-inch round, so your cake will be thinner. Bake at the same temperature but reduce the time by about 5 minutes — check for doneness at 75% of the original time.
How do I convert a round cake recipe to a square pan?+
A square pan of the same edge length as a round pan's diameter holds about 25% more batter. Either increase the recipe by 25% to maintain layer thickness or use the original recipe and reduce the bake time by 5–8 minutes.
How do I convert an 8-inch round recipe to a 9×13 sheet pan?+
A 9×13 pan holds 14 cups vs the 8-inch round's 6 cups. Multiply the recipe by 2.3× for a similar thickness, or use the original recipe as a thinner sheet cake. Reduce bake temperature by 25°F (15°C) and bake time by 25–35%.
Why does my cake sink in the middle when I use a different pan?+
Most often this means the pan was overfilled or the temperature was too high for the new pan size. When converting to a larger or shallower pan, drop the temperature by 25°F (15°C). Also confirm you're checking doneness with a toothpick or internal temperature, not just relying on the original time.
How do I measure my pan's actual volume?+
Fill the pan with water using a measuring cup until you reach the level you'd normally fill batter to (usually 2/3 full). The total cups poured in is your pan's working volume — far more accurate than using the printed dimensions.