If you live above approximately 900 metres (3,000 feet) in altitude, standard baking recipes may not work as written. Lower atmospheric pressure means gas bubbles expand faster, liquids evaporate more quickly, and the boiling point of water drops — all of which affect the texture, rise, and structure of baked goods.
Why High Altitude Changes Baking
At sea level, air pressure is about 101 kPa. At 1,500 metres (5,000 feet), it drops to around 84 kPa. This lower pressure means:
- Leavening gases expand faster: Carbon dioxide produced by baking powder/soda expands more quickly, which can cause baked goods to rise too fast and then collapse.
- Water evaporates faster: This leaves baked goods drier than intended.
- Boiling point drops: Water boils at about 95°C (203°F) at 1,500m instead of 100°C (212°F), affecting caramel, candy, and custard making.
General Adjustments by Altitude
| Altitude | Reduce leavening | Reduce sugar | Add liquid |
|---|---|---|---|
| 900–1,500m | Reduce by 10–15% | Reduce by 1 tbsp | Add 1–2 tbsp |
| 1,500–2,400m | Reduce by 15–25% | Reduce by 1–2 tbsp | Add 2–4 tbsp |
| 2,400m+ | Reduce by 25% | Reduce by 2–3 tbsp | Add 3–4 tbsp |
Practical Adjustments
For cakes:
- Reduce baking powder by 25% and add an extra 1–2 tablespoons of liquid per cup of flour.
- Increase oven temperature by 15°C (25°F) to help set the structure faster.
- Increase flour by 1 tablespoon per cup to strengthen structure.
For cookies:
- Flatten cookies slightly before baking — they spread more quickly at altitude.
- Reduce sugar slightly and add a little extra flour.
For yeast breads:
- Reduce rising time — dough rises faster at altitude. Punch down after 50% of normal rise time.
- Add slightly more flour for a stiffer dough.
A Note on Testing
High-altitude baking often requires trial and error — the exact adjustments depend on your specific altitude, recipe, and oven. Start with smaller adjustments and note what works.