Thin air, two consequences
Atmospheric pressure falls with elevation — roughly half a pound per 1,000 feet:
| Elevation | Air pressure |
|---|---|
| Sea level | 14.7 psi |
| 5,000 ft | 12.3 psi |
| 10,000 ft | 10.2 psi |
Everything else follows from two consequences. Liquids evaporate faster and boil at lower temperatures, so batters dry out and anything simmered cooks cooler and slower. And leavening gases expand more quickly, because there's less air pressing back on them — so a cake races upward, stretches its cell structure past what it can hold, and collapses. Every adjustment below is aimed at one of those two.
Cakes: the published table
Colorado State University Extension publishes the reference table US extension services and the USDA point to. Its bands are 3,500–6,500 ft, 6,500–8,500 ft, 8,500–10,000 ft — worth stating, because many recipe sites reprint a 3,000/5,000/7,000 version that doesn't match the publication. Below 3,000 ft, CSU says sea-level recipes need no modification at all.
| Adjustment | 3,500–6,500 ft | 6,500–8,500 ft | 8,500–10,000 ft |
|---|---|---|---|
| Reduce baking powder, per tsp | ⅛ tsp | ⅛–¼ tsp | ¼ tsp |
| Reduce sugar, per cup | 0–1 Tbsp | 0–2 Tbsp | 1–3 Tbsp |
| Increase liquid, per cup | 1–2 Tbsp | 2–4 Tbsp | 3–4 Tbsp |
Notice they're ranges. That's not vagueness — high-altitude baking genuinely is trial and error, and CSU's own instruction is to try the smaller adjustment first. The calculator applies these to your actual amounts:
Oven temperature
+15–25°F
Adjustment band: 3,500–6,500 ft · water boils at about 202°F here
Your recipe (optional — leave blank to skip)
Sugar
1½ cups → reduce by 0–1½ Tbsp
Liquid
1 cup → add 1–2 Tbsp
Baking powder / soda
2 tsp → reduce by ¼ tsp = 1¾ tsp
Try the smaller adjustment first — CSU Extension's own advice. Many sea-level recipes need little or no change, so don't assume yours will fail before you've baked it once.
Source: CSU Extension, High Altitude Food Preparation . The table stops at 10,000 ft, and our calculator says so rather than extrapolating past it.
Bread: watch the dough, not the clock
Yeast bread is the one case where the cake table mostly doesn't apply. Altitude's pronounced effect here is on rise time — dough doubles faster in thin air, and a rise that finishes early hasn't developed the flavour a slower one would. The fixes CSU gives are about time and handling rather than ratios:
- Use a little less yeast, or punch the dough down and let it rise a second time.
- Let dough rise until just doubled. Over-proofing at altitude gives a heavy, dry or misshapen loaf, or one that collapses in the oven.
- Flours are drier in high, dry climates and absorb more liquid — so slightly less flour, or a little more liquid, to reach the same dough consistency. For bread-machine loaves CSU suggests decreasing yeast by ¼–½ tsp per 2½ tsp packet and adding 1–2 Tbsp of liquid per cup of flour.
- Tracking a formula while you adjust? The baker's percentage calculator keeps hydration and salt honest while you change the flour and water.
Everything governed by boiling point
Frying, candy, jelly and anything simmered follow water's boiling point rather than the cake table — and that falls steadily with elevation:
| Elevation | Water boils | Lower frying oil by | Lower candy finish by | Cook jelly to |
|---|---|---|---|---|
| 3,000 ft | 206°F | 9°F | 6°F | 214°F |
| 5,000 ft | 203°F | 15°F | 10°F | 211°F |
| 7,500 ft | 198°F | 23°F | 15°F | 206°F |
| 10,000 ft | 193°F | 30°F | 20°F | 201°F |
The jelly column is the most useful trick in the whole guide: rather than trusting any chart, boil a pot of water, read its temperature, and cook jellies to 8°F above that. It's self-calibrating, so it's right at any elevation including yours. The same logic applies to candy — test your water first, then reduce the recipe's finish temperature by the difference from 212°F.
Simmered and boiled foods simply take longer, since they're cooking cooler: meats braised or simmered can need about a quarter more time at 5,000 ft. Oven roasting, though, is unaffected — an oven's temperature doesn't care about air pressure. Converting a recipe's oven temperature between scales is a different question, and the oven temperature converter handles °F, °C, gas marks and fan.
Cookies, pastry and the things that barely change
- Cookies frequently need nothing. Many recipes carry more sugar and fat than strictly necessary even at sea level, which is what makes them sprawl. If yours spread: a slightly hotter oven, a little less baking powder or soda, a little less fat and sugar, and a little more liquid and flour.
- Pie crusts are largely unaffected — slightly more liquid may improve the texture, and that's the whole adjustment.
- Angel food and sponge cakes are the fragile exception, since their leavening is trapped air. Beat the whites only to shiny peaks that droop slightly, never stiff and dry, and strengthen the structure with less sugar, more flour and a hotter oven.
- Rich cakes can be helped by reducing shortening 1–2 Tbsp; fat, like sugar, weakens cell walls. An extra egg adds structure and moisture and can stop a rich cake falling.
The instruction most pages skip
CSU's guide opens its practical notes with advice worth repeating in full: don't assume your sea-level recipe will fail. Try it as written first — it may need little or no modification. When it does need help, start with the smaller adjustment in the range, change one thing at a time, and write down what you did. Repeated experiments with one specific recipe will beat any general table, including the one on this page.