Why altitude changes baking
At higher altitude the air pressure is lower. That has three effects on baking:
- Water boils at a lower temperature, about 203 °F at 5,000 feet instead of 212 °F at sea level, so moisture evaporates faster.
- Gases expand more, so the bubbles from baking powder and beaten eggs grow too large, rise too quickly and then collapse.
- Sugar becomes more concentrated as water evaporates, which weakens the structure of the batter.
The result is often a cake that domes, sinks in the middle, or turns out dry and coarse.
The adjustments
The calculator applies the usual guidance from US extension services and flour mills for cakes, quick breads and muffins, in three altitude bands:
| Adjustment | 3,000–4,999 ft | 5,000–6,999 ft | 7,000 ft and up |
|---|---|---|---|
| Baking powder or soda | −⅛ | −3⁄16 | −¼ |
| Sugar, per cup | −½ Tbsp | −1 Tbsp | −2½ Tbsp |
| Liquid, per cup | +1½ Tbsp | +3 Tbsp | +3½ Tbsp |
| Oven temperature | +15 °F | +20 °F | +25 °F |
| Baking time | about −17% | about −22% | about −27% |
Below 3,000 feet, recipes usually work as written.
Worked example
A cake recipe calls for 2 tsp baking powder, 1 cup sugar and 1 cup milk, baked at 350 °F for 30 minutes. At 5,000 feet:
| Ingredient or setting | Adjusted |
|---|---|
| Baking powder | about 1⅝ tsp (1.63) |
| Sugar | about 15 Tbsp (0.94 cup) |
| Liquid | about 1 cup + 3 Tbsp (1.19 cups) |
| Oven | 370 °F |
| Time | start checking at about 23 minutes |
The hotter oven sets the cake’s structure before the bubbles over-expand, and the extra liquid makes up for faster evaporation.
Other tips
- Eggs: for rich cakes, an extra egg or an extra egg white strengthens the structure.
- Flour: at 7,000 feet and above, add 1 to 2 tablespoons of flour per cup for more structure.
- Pans: fill them only half full, since batter rises higher.
- Yeast breads: they rise faster at altitude; shorten rising times or use about a quarter less yeast, and let the dough rise twice.
- Candy and sugar syrups: lower the target temperature by about 2 °F for every 1,000 feet, because water boils at a lower temperature.
These are starting points. Every recipe behaves a little differently, so note what you changed and adjust after the first bake.