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. Julia

    I love you PJ! I knew there was something about you – and now I can put my finger on it. “just say no to sugar-sprinkled stars, heavily iced reindeer, and anything – ANYTHING – draped in dragées”
    Merry Christmas, happy baking and thank you for making me feel a little better about HATING to decorate all those fancy cookies!

  2. cookiesfromhome

    This one is the perfect holiday gift for near and dears. Thanks for sharing an easy method of baking these brownies.

    Cookie Gifts

  3. Sallie

    Bless you and all your children for this enlargement on the recipes. This will be quite useful for big group functions and bake sales.

  4. Gwenn Lasswell

    YAY! I’m so doing this…after I scrape off the overbubbling of a recent blueberry cobbler. What a mess! You obviously have a gift for math (I have mathematical kids and hubby. Calculations for me require only a phone call) so could you devise a formula to determine the expected bubble over? Example: If I make cobbler with a raw mass of,say, 2 qts. How large of a container should I be using to contain the inevitable bubbling up that WILL occur. This might be something pros already know but I don’t. I know if I ask hubby this question he won’t understand. At the mention of cobbler his eyes would glaze over and we lose him.

    1. Susan Reid

      Gwenn, the best thing to do is go by the law of 2/3. If you know your cobbler’s volume is 2 quarts, your baking vessel’s capacity should be 3 quarts to the rim. That will give you the headspace you need. Susan

    1. The Baker's Hotline

      Angela, this is why scales are so useful! The best way to achieve half an egg is to scramble it lightly, just enough to get a uniform consistency, and then take half this amount. Barb@KAF

  5. Vivian

    Ouch, math makes my head hurt. But I certainly appreciate that you did it for me! I keep some dried egg powder on hand for times I need a “half” egg. 🙂


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