Two 8-inch Rounds to 9×13 Rectangle
Two layers
12.6 cups total
Single layer
10.9 cups
Use 87% of your ingredients
Good News:
Similar depth means minimal adjustment needed!
Why This Conversion Works Well
Volume Comparison
Depth Analysis
Original layers:
Each 1.5-2" deep (standard)
New single layer:
About 1.8" deep (very similar!)
✓ Nearly identical depth = easy conversion
Simple Adjustments Needed
Same Temperature
Keep at 350°F. The similar depth means no temp change needed.
Add 5-8 Minutes
Single thick layer vs two thin. If layers took 25 min, expect 30-33 min.
Even Distribution
9×13 has corners that 8" rounds don't. Spread batter evenly.
Pan Converter
Quick Recipe Math
Original (Two 8" rounds)
- 3 cups flour→ 2⅔ cups
- 4 eggs→ 3½ eggs (use 4)
- 1 cup butter→ ⅞ cup (7oz)
Baking Comparison
Why Choose This Conversion?
🎉 Party Efficiency
- • One pan to transport vs. two
- • Easier serving: uniform squares
- • No worry about matching layer heights
- • Faster cooling time
⏱️ Time Savings
- • Single bake session
- • No waiting for oven availability
- • Less dishes to wash
- • Simpler frosting application
From Layers to Sheet: What Changes?
Texture Considerations
Original Layer Cake
Frosting between layers adds moisture to every bite. The cake-to-frosting ratio is balanced throughout.
Converted Sheet Cake
Only top frosting means the cake itself must be moister. Consider adding an extra egg yolk or 2 tbsp sour cream.
💡 Moisture Boost Formula
For every 2 cups of flour in your recipe, add:
- • 2 tablespoons sour cream OR
- • 1 extra egg yolk OR
- • 3 tablespoons buttermilk (reduce other liquid by 2 tbsp)
Professional Baker's Secret
The "Sheet Cake Soak" Technique
Professional bakers know that sheet cakes can dry out faster due to their larger surface area. Here's their secret:
Simple Syrup Soak
- • ¼ cup sugar + ¼ cup water
- • Heat until dissolved
- • Add 1 tsp vanilla extract
- • Brush over warm cake
This adds moisture without making the cake soggy, and helps frosting adhere better.
Pro Tips for Layer-to-Sheet Conversion
Missing the layers?
Cut the 9×13 in half crosswise after cooling. Stack with frosting between for a rectangular layer cake!
Perfect corners
Use an offset spatula to push batter into corners. 9×13 pans tend to have rounded corners that need extra attention.
Doneness test
Test the center AND a spot 2 inches from the edge. In rectangles, these can have different doneness levels.