High altitude baking calculator

Why do cakes fail at high altitude?

Air pressure drops as you go up — from 14.7 psi at sea level to 12.3 psi at 5,000 feet, according to Colorado State University Extension. Leavening gases expand faster and water evaporates faster, so a cake can over-rise, turn coarse or fall.

How much do I change a cake recipe?

CSU Extension’s cake table, for each teaspoon of baking powder or soda, each cup of sugar and each cup of liquid: at 3,500–6,500 ft use ⅛ tsp less leavening, 0–1 Tbsp less sugar and 1–2 Tbsp more liquid; at 6,500–8,500 ft ⅛–¼ tsp less, 0–2 Tbsp less and 2–4 Tbsp more; at 8,500–10,000 ft ¼ tsp less, 1–3 Tbsp less and 3–4 Tbsp more.

How much do I raise the oven temperature?

By 15 to 25 °F, to set the batter before the gas cells stretch too far (CSU Extension). The cake may bake faster, so start checking early.

Example

At 5,000 ft, a cake with 2 tsp baking powder, 1½ cups sugar and 1 cup milk at 350 °F becomes 1¾ tsp baking powder, 1½ cups sugar minus up to 1½ Tbsp, 1 cup milk plus 1–2 Tbsp, baked at 365–375 °F.

At what temperature does water boil at altitude?

CSU Extension gives about 212 °F at sea level, 208 °F at 2,000 ft, 203 °F at 5,000 ft, 198 °F at 7,500 ft and 193 °F at 10,000 ft. Between those points the calculator reads the table in a straight line.

Does the cake table also work for cookies and bread?

No. The table is written for cakes. CSU Extension treats cookies and yeast breads separately: cookies are often fine as written or need small changes (a slightly hotter oven, a little less leavening, fat or sugar, a bit more liquid and flour). Use this tool for cakes and cake-like recipes, and change one thing at a time for the others.

Should I make all the changes at once?

Start with the smaller end of each range, bake, and adjust from there: the ranges are starting points, and recipes with a lot of leavening or sugar react more strongly. Note what you changed, so that the next bake can move one setting at a time. The calculator shows a range for each setting for this reason.

How the adjustments work

The table works on three quantities per recipe: the baking powder or soda (per teaspoon in the recipe), the sugar (per cup) and the liquid (per cup). At 3,500–6,500 feet, 6,500–8,500 feet and 8,500–10,000 feet the guide gives a range for each, as in the FAQ above. The calculator picks the band from your elevation, multiplies the ranges by the amounts in your recipe, and adds 15–25 °F to the oven temperature. Below 3,500 feet, the table does not apply.

Worked example

A cake that calls for 2 tsp baking powder, 1½ cups sugar and 1 cup of milk, baked at 350 °F, becomes at 7,500 feet: 1.50 to 1.75 tsp baking powder (⅛ to ¼ tsp less per teaspoon), 1.31 to 1.50 cups sugar (0 to 3 Tbsp less), 1.13 to 1.25 cups of milk (2 to 4 Tbsp more) and an oven at 365–375 °F. A cake pan filled only partway is also advised by CSU Extension, since a batter that over-rises is the main failure.

Mistakes to avoid

Changing only the oven temperature, or only the leavening, is the first mistake; at altitude the problem is the balance between gas, structure and moisture, and the three adjustments work together. The second is applying the full correction twice, to a recipe that is already written for high altitude. The third is forgetting that the cake table is not a boiling-water rule: water boils at about 203 °F at 5,000 feet and 198 °F at 7,500 feet, against 212 °F at sea level, and the table says nothing about recipes that depend on boiling or simmering. Check a cake for doneness by sight and touch, because it may bake faster in the hotter oven.

Sources: Colorado State University Extension, “High Altitude Food Preparation” (P. Kendall; cake adjustments, oven temperature, boiling points, cookies and breads). Related tools: candy temperature and baker's percentage calculators.