How many box cakes for a 15x21x2 pan?

It's impossible to say exactly how many box cakes you'll need for a 15x21x2 pan without knowing:

* The size of your box cakes: Box cake mixes vary in size. Some are meant for 9x13 inch pans, others for 8x8 inch pans.

* The desired height: Do you want the cake to fill the pan completely or just a portion of it?

Here's how to figure it out:

1. Calculate the pan's volume: 15 inches x 21 inches x 2 inches = 630 cubic inches.

2. Calculate the volume of your box cake: Find the dimensions of your box cake mix (usually stated on the package) and multiply length x width x height.

3. Divide the pan's volume by the box cake's volume: This will give you a rough estimate of how many boxes you need.

For example:

* If your box cake mix makes a 9x13 inch cake (approximately 117 cubic inches), you would need about 630/117 = 5.4 boxes.

* You would round up to 6 boxes to ensure you have enough batter.

Remember:

* This is just an estimate. You may need more or less batter depending on the specific box cake mix and your desired cake height.

* You can always make a smaller cake and freeze the leftover batter for another time.

Tip: It's always best to err on the side of having too much batter rather than not enough!