Simple Math for High-Altitude Baking
It’s a sad thing when you put the effort into baking a cake and the middle collapses, leaving you with a donut shape instead of a domed cake. Even worse if it tastes dry and overbaked. Even baking a boxed cake or brownies can be disappointing because it’s rare to find altitude adjustments in the instructions— some do, most don’t.
There are several factors going on that can affect your baking at elevation. Since Bozeman is just under 5,000 feet above sea level, our adjustments for high-altitude baking are slight, but as you go up in elevation, the ramifications of less air pressure are magnified, and you need to increase your adjustments. For reference, see King Arthur Flour’s “High-Altitude Baking” available at kingarthurflour.com.
High elevation makes for less air pressure, which causes several things to happen:
Things “poof ” sooner so you need less leavening, more structure in the form of flour, and a higher oven temperature to set the poof before it collapses. Use ⅛ teaspoon less baking powder or baking soda per cup of flour, add an extra tablespoon of flour for each cup of flour, and increase the oven temperature about 15 degrees F.
Things bake faster, so reduce baking time by about 5 minutes per 30 minutes in the original recipe.
Liquids evaporate faster, so use 1 tablespoon more of the liquid called for in the recipe (milk, oil, water, eggs) for each cup of flour. Also, quickly evaporating liquids concentrate sugar, so you need a little bit less sweetener; use 1 tablespoon less sugar for each cup of fl our.
High elevation also affects jam and candy-making, so target temperatures for soft-ball, hard-ball, hard crack, etc. need to be adjusted down. Since our boiling point of water is lower than 212 degrees (a good estimate is 2 degrees lower per 1,000 feet above sea level), adjust all target temperatures down by 10 degrees in Bozeman. (So, the soft-ball stage is 225–230 degrees versus the sea level target of 235–240).
Baking at altitude can require an adjustment but a little simple math is so worth the effort.
