Big batch brownies and bars: the fastest, easiest way to make dozens of holiday treats at once

When you get past the glitter and glam of holiday cutout cookies, what are you left with? Often, a rather insipidly sweet and undistinguished cookie.

Which is why I just say no to sugar-sprinkled stars, heavily iced reindeer, and anything – ANYTHING – draped in dragées.

Big Batch Brownies and Bars via @kingarthurflour

Instead, I like to gift my nearest and dearest with undistinguished-looking but absolutely delicious brownies and bars. Which means I turn to big batch brownies and bars: the surefire way to save time, money, and lots of colored icing-induced irritation.

What’s the best way to make lots and lots of brownies and bars all at once?

First, do some easy math.

Find a recipe that fills a 9″ x 13″ pan, double it, and bake it in a half-sheet pan (13″ x 18″), right?

Wrong. And here’s why –

While the classic dimensions of a half-sheet pan are 13″ x 18″ (double the size of a 9″ x 13″ pan), in reality most half-sheet pans measure about 12″ x 17″, inside dimensions.

Plus, a half-sheet pan is only 1″ deep, while a typical 9″ x 13″ pan is 2″ deep. So a half-sheet pan actually offers a lot less baking real estate – both horizontally, and vertically – than you might think.

Doubling that high-rising brownie recipe and sticking it in a half-sheet pan offers the potential – nay, the likelihood – of half-baked batter bubbling over the 1″ sides of the pan onto the oven floor. NOT a pretty picture.

But don’t give up on your handy half-sheet. You can still start with your favorite 9″ x 13″ bar recipe; but instead of doubling it for the larger pan, increase all of the ingredients in your 9″ x 13″ recipe by 50%.

This is most easily done with a scale. And a tiny bit of math.

Big Batch Brownies and Bars via @kingarthurflour

Choose your recipe.

I’ve decided on a simple stir-together one-bowl brownie recipe, Quick and Easy Fudge Brownies.

The recipe calls for a 9″ x 13″ pan. Check.

Next, increase all of the ingredient amounts by 50%.

Easiest math? Metric. I toggle to the gram weights at the top of the online recipe, then print a copy. From there, it’s simple to increase everything by half.

But what about the eggs, you ask. How did 3 large eggs, increased by 50%, become 224g eggs?

Serendipitously, a typical large egg weighs about 50g. So 3 eggs weigh 150g. Times 1 1/2 = 225g eggs. (So OK, I came up with 224g; it’s a boring story involving decimal points and rounding…)

Big Batch Brownies and Bars via @kingarthurflour

Then, mix and bake your big batch brownies.

Make the batter. Spread it in the pan. Bake.

I’ve discovered that using this method doesn’t change the baking time, though you’ll probably want to stick with the shorter time if the recipe gives a range. And while it results in slightly thinner bars, the difference isn’t appreciable.

Big Batch Brownies and Bars via @kingarthurflour

Finally, cool and cut into squares.

You’ll get anywhere from 4 dozen largish (2″) squares to 88 smaller (1 1/2″) squares.

I prefer smaller squares for gift-giving. Keeping things small allows you to offer a wider array of treats on one plate. Plus, c’mon, everyone you know is trying to keep weight gain in check over the next few weeks – give your friends a hand by keeping portion sizes small.

One final note: what if your recipe calls for an 8″ x 8″ pan, or 9″ x 9″?

Back to the chalkboard. The interior surface of a half-sheet pan measures 204 square inches (12″ x 17″). Increasing a 9″ x 13″ pan by 50% = 175 1/2″. Since we know 175 1/2″ is the “sweet spot” – bars fill the pan nicely, without overflowing – that’s the number we’re going for with other size pans.

Doubling a 9″ x 9″ pan recipe = 162″, about 8% less than 175 1/2″. Seems like it should work.

Tripling an 8″ x 8″ pan recipe = 192″, about 9% more than 175 1/2″. You MIGHT be risking too much batter (overflow), but give it a try. Put a pan underneath to catch any potential drips, and you’ll be good to go.

Big Batch Brownies and Bars via @kingarthurflour

Good. To go – right onto your holiday gift plate.

Now go forth and bake!

PJ Hamel

PJ Hamel grew up in New England, graduated from Brown University, and was a Maine journalist before joining King Arthur Flour in 1990. PJ bakes and writes from her home on Cape Cod, where she enjoys beach-walking, her husband, two dogs, and really good food!


  1. Kimberly Aldridge

    I have a Nordicware 2-inch deep half sheet pan (13×18). Would I be safe doubling a 9×13 bar cookie recipe for this pan? Or would you still advise increasing the recipe by 50%?

    1. The Baker's Hotline

      Hi there, Kimberly! A 2″ x 13″ x 18″ pan will hold approximately the equivalent of two 9″ x 13″ pans, so you should be safe to go ahead and double your recipe if you’re using that pan. For the first time around, we’d recommend only filling the pan 2/3 full just to be safe though. Happy baking! Morgan@KAF

  2. Mary

    Since December 2015, no else but me must have made these brownies and read the weight for sugar as 596 grams. There is a significant difference between 596g and 576 g which made the brownies hard as a rock. Woe is me who trusted the formula as written for big batch brownies.

    BTW, I do use a scale and appreciate that you offer grams as an option which has been my choice for many years.

    1. The Baker's Hotline

      We’re sorry that happened to you, Mary! The recipe in question has been updated in the last few years. We hope you’ll have more luck with the newer version, as written on the recipe page. Happy baking! Kat@KAF

  3. Mary

    the weight of sugar appears to be incorrect. one-half of 350 is 175. Adding 175 to 350 is 525g not 596. So sorry I didn’t verify the formula. A whole pan of hard as a rock brownies in the trash.

    1. The Baker's Hotline

      Hi, Mary! This blog post is based on an older version of the recipe, as you can see in the photo. The recipe PJ printed up here and used called for 397 grams of sugar. 150% of that is 596 grams. You’ll notice that the salt is also different now. Feel free to do the math based on the newer version of the recipe, which comes out exactly as you’ve indicated. Happy baking! Kat@KAF

    1. The Baker's Hotline

      Hi there, Meredith! Yes, if you have a full-size baking sheet (also called a full sheet pan, usually 18″ x 26″) you could just double the recipe. Happy baking! Morgan@KAF

  4. Dwan

    I don’t have a scale so can you send me the recipe for brownies and bars for half sheet pan in cups,tbsp,tap please thank you.

    1. The Baker's Hotline

      Thanks for checking out this post, Dwan. We’re unable to calculate the recipe for you, but you can view this and all of our recipes either in volume, ounces, or grams. Here is this recipe by volume, and you can calculate for your half sheet pan by doing a 1 1/2 times batch. Happy baking! Annabelle@KAF

    1. PJ Hamel, post author

      Vanilla is routinely added to many baked goods to enhance their flavor, if only quite subtly in certain instances. You can leave it out if you like. PJH

    2. Marz.B

      It says one tablespoon. Capital ‘T’ meaning tablespoon, lower case ‘t’ being teaspoon. So the math is correct, if you multiply 2 teaspoons of vanilla by 50% you have 3 teaspoons and 3 teaspoons is equal to 1 tablespoon. I hope that’s cleared it up for you.

Leave a Reply to Annemarie Cancel reply

Your email address will not be published. Required fields are marked *