Baking Pan Conversions Made Easy

Part 4 of my Baking Basics series: These handy charts will help you determine how much batter and how much of each ingredient you need for different sized and shaped baking pans. We’re talking about dimensions, volume and surface area for the best results!

Imagine this: You find the recipe of your dreams, but it calls for a 13″ x 9″ rectangular pan, and you don’t have that size. Don’t panic! With a little math, you can figure out how to convert the recipe for the size pan you do have.

A few tips for converting recipes

• Don’t fill your pan more than 2/3 full. You might do the math and discover your pan will work, but just barely. If you have to fill the pan more than 2/3 full, find a different pan (or maybe even split the recipe in half and make it in two batches, if it works). Otherwise, you’re looking at batter that might overflow and find it’s way to being burned into the bottom of your oven.
• Larger pans = longer bake time. Mind you, this isn’t a 100% of the time kind of rule, but it’s a good guideline. More batter means more to bake, which will in turn likely mean slightly longer bake times.
• More shallow batter depth = shorter bake times. Read below for the details, but if your conversion has resulted in a slightly more shallow depth than the original recipe would have in the designated pan, you’ll need to adjust for a shorter baking time to avoid drying it out and overbaking.
• Measure your pans inside edge to inside edge. If you’re not sure if the pan dimensions, always measure on the inside edges of the pan so that you’re not including the thickness of the edges in your measurement.
• Don’t try to bake in a pan bigger than your oven can accommodate! Hopefully this goes without saying, but don’t do a conversion to a pan size your oven can’t handle. I’ve seen some tiny ovens in tiny apartments, and… well, those of you using them are a stronger person than I am. And I’d love to see your tiny ovens and the amazing things you make in them so that I can marvel at it all, so please send pictures my way, kthx.

Guideline for conversions

You can do a little quick math to help figure out the conversion of one pan size to another using this as a guideline:

1″ = 1 cup = 240mL

So for example, if you have a recipe that calls for a 13″ x 9″ rectangular pan and you want to halve the recipe, but aren’t sure if that will fit in your 8″ x 8″ pan:

13″ x 9″ x 2″ pan = 14 cups
8″ x 8″ x 2″ pan = 8 cups

So if you halved the recipe, you’d have 7 cups – and that fits in your 8″ x 8″ pan. Hooray! But something you’ll want to take into consideration is the surface area as well – we’ll dig in to that in a bit.

Rectangular & Square Pan Dimensions

Round Pan Dimensions

Loaf Pan Dimensions

Springform Pan Dimensions

Bundt Pan Dimensions

Calculating pan surface area

Adjusting for volume is a large part of successfully converting a recipe for a different pan size, but surface area is important, too! The depth of what you’re baking can result in a different baking time, and the last thing you want is to put all this work into converting the recipe, making the recipe, and then baking it too long. Dry cake makes Leslie sad.

First you need to calculate the surface area of each pan:

Surface area for rectangular and square pans
Length x width = surface area

Surface area for round pan
3.14 x radius² = surface area

And then you can use this formula:

Large pan area ÷ smaller pan area = number of times needed to multiply the recipe for the same depth in the larger of the two pans

Calculating and comparing surface areas

That was a lot of words – let’s use the same example I used above. First you need to calculate the surface area of each pan:

13″ x 9″ pan = 117 square inches
8″ x 8″ pan = 64 square inches

And now we use the formula above to determine the ratio:

117 ÷ 64 = 1.83

So if you’re trying to reduce the original recipe for the smaller square pan, you actually want to divide each of the ingredients by 1.83, and not 2. Obviously that makes the calculations of reducing each ingredient challenging, so take that with a grain of salt.

If you decide to keep the math simple and just divide the recipe in half, you’ll end up with a slightly deeper batter, which may require adjusting the baking time to be a little longer.

Still with me? Okay, let’s try a slightly more complicated example.

Converting from a rectangular pan to round pan

Now let’s do the same conversion from a 13″ x 9″ pan, but to a round 8″ x 2″ pan.

13″ x 9″ pan = 13 x 9 = 117 square inches
8″ x 2″ pan = 3.14 x 4² = 50.24 square inches
117 square inches ÷ 50.24 square inches = 2.33

So in this case, you’d want to reduce the recipe by a little more than half. You’ll end up with a slightly more shallow batter, which may require adjusting the baking time to be a little less.

Below are the surface area calculations of the most common pan sizes for your reference so you have one less bit of math to do.

Rectangular & Square Pan Surface Areas

Formula: Length x width = surface area

Round Pan Surface Areas

Formula: 3.14 x radius² = surface area