What temperature does water boil at?

Water boiling is the most fundamental kitchen temperature, but it varies based on altitude, atmospheric pressure, and what's dissolved in the water. The "212°F = boiling" rule is true ONLY at sea level with pure water and standard atmospheric pressure. Understanding the variables matters for cooking, canning, sterilization, and baking.

The standard boiling point:

• Sea level (0 ft elevation), 1 atm pressure, pure water: 212°F (100°C)
• Defined as: vapor pressure of water = surrounding atmospheric pressure
• At this point, liquid → gas transition happens throughout the water (rolling boil)

The altitude effect (most important variable):

Atmospheric pressure decreases with altitude. Lower pressure = water needs less heat to boil. Approximation: boiling point drops ~1°F per 500 ft of altitude gain.

What this means for cooking:

At high altitudes, water boils at lower temperatures, so foods take longer to cook. At 5,000 ft (Denver): - Pasta: 1-2 minutes longer to al dente - Hard-boiled eggs: 12-14 min instead of 10 - Rice: needs more water, longer time, or pressure cooker - Boiling meat / blanching vegetables: noticeably longer - Canning: requires longer processing time or higher temperatures

At 7,500 ft+, baking also changes (lower air pressure affects rising — but that's separate from boiling).

Pressure effect (pressure cookers):

Pressure cookers raise the boiling point by trapping steam: - 15 psi pressure: water boils at 250°F (121°C) - 10 psi: 240°F (115°C) - 5 psi: 227°F (108°C) - This is why pressure cookers cook 2-3× faster than regular pots

Conversely, vacuum chambers (sous vide circulators that pull vacuum) drop boiling points dramatically.

Dissolved solutes effect:

• Salt: 1 tsp salt per quart raises boiling point ~0.3°F — negligible for cooking
• Sugar: 1 cup sugar per quart raises boiling point 1-2°F — noticeable in candy-making
• Heavy syrup at 220°F (sea level) = 6°F above water boiling = sugar concentration ~50% by weight
• This is why candy-making relies on temperature, not time

Simmer vs. boil (the chef distinction):

• Hard rolling boil: 212°F (sea level), continuous large bubbles bursting at surface
• Boil: 212°F, bubbles continuously at surface
• Simmer: 180-205°F (82-96°C), small bubbles, gentle motion
• Bare simmer (poach): 160-180°F (71-82°C), barely moving, isolated bubbles
• Poach (eggs): 180-190°F (82-88°C), no bubbles to surface, very gentle motion

Why simmer not boil for stocks:

A rolling boil at 212°F: - Emulsifies fat into water (cloudy stock) - Breaks down delicate proteins - Can make meat tough (denaturing proteins quickly) - Loses delicate flavors via faster evaporation

Simmer at 180-200°F: - Fat stays separate (skimmable for clear stock) - Proteins denature gently - Meat tenderizes vs. toughens - Delicate flavors preserved

Temperature ranges for water-based cooking:

Boiling point of other common liquids (cooking reference):

Common altitude-cooking adjustments:

• Boiling water for pasta at 5,000 ft: add 1-2 min cooking time
• Eggs at altitude: 12-14 min for hard boiled (vs. 9-10 sea level)
• Rice cooker at altitude: add extra water, extra time, or use pressure cooker
• Canning at altitude: longer processing time per USDA charts (essential for safety)
• Boiled potatoes: noticeably longer at altitude

Don't: - Assume water boils at 212°F regardless of location - Confuse "rolling boil" with "simmer" for delicate cooking - Cook meat at rolling boil (toughens proteins) - Use less time for high-altitude boiling (food won't be safe or cooked through) - Try to "boil away" alcohol completely (some alcohol can persist even with long simmering)

Common mistakes:

• High altitude under-cooking: assume sea-level times; food undercooked
• Stock turning cloudy: boiled too vigorously instead of simmering
• Watery sauce: confused simmer (200°F) with boil (212°F), didn't reduce
• Tough meat in soup: rolling boil instead of gentle simmer

Cross-reference: see /pages/how-to-convert/celsius-to-fahrenheit for temperature conversions + /pages/what-temperature-for/cooking-chicken for cooking temperatures + /pages/how-long-does/cooked-rice for altitude-affected timing.

Most published references (NIST Chemistry WebBook, Harold McGee "On Food and Cooking", USDA canning guides, Modernist Cuisine, J. Kenji López-Alt "The Food Lab") converge on 212°F sea-level baseline with altitude/pressure/solute variations as documented above.