Calculate Water Boiling Temperature
Estimate the boiling point of water from altitude or atmospheric pressure.
What is the boiling point of water?
Most people learn that water boils at 100°C (212°F), but that value is only true at standard sea-level atmospheric pressure (1 atm). If pressure changes, boiling temperature changes too. This is why water boils at a lower temperature in mountain towns and at a higher temperature in pressure cookers.
Why boiling point changes with altitude and pressure
Boiling happens when vapor pressure matches surrounding pressure
A liquid boils when its vapor pressure equals the pressure pushing down on its surface. At higher elevations, air pressure is lower, so water needs less thermal energy to boil. That means the boiling point drops.
At lower elevations (or in pressurized systems), pressure is higher, so water must reach a higher temperature before boiling starts.
How to use this boiling point calculator
- Select whether you want to enter altitude or pressure.
- Enter your value and unit.
- Click Calculate Boiling Point.
- Read the estimated boiling point in both Celsius and Fahrenheit.
Equations used in this calculator
1) Altitude to pressure
For altitude-based input, pressure is estimated with a standard atmosphere approximation:
P (kPa) = 101.325 × (1 − 2.25577 × 10−5 × h)5.25588
where h is altitude in meters.
2) Pressure to boiling temperature
The calculator then uses an Antoine-equation form for water (common engineering approximation):
T (°C) = B / (A − log10(PmmHg)) − C
with constants A = 8.07131, B = 1730.63, and C = 233.426.
Typical boiling points by elevation
| Elevation | Approx. Pressure | Boiling Point of Water |
|---|---|---|
| 0 m (Sea level) | 101.3 kPa | 100.0°C (212.0°F) |
| 1,000 m | 89.9 kPa | 96.8°C (206.2°F) |
| 2,000 m | 79.5 kPa | 93.5°C (200.3°F) |
| 3,000 m | 70.1 kPa | 90.2°C (194.4°F) |
Practical uses
- Cooking: Understand why food takes longer to cook at high elevations.
- Brewing: Better coffee and tea extraction planning at different altitudes.
- Science and lab work: Estimate expected boiling temperatures for experiments.
- Engineering: Support rough thermal calculations where pressure varies.
Accuracy and limitations
This calculator is designed for practical estimates, not high-precision thermodynamic modeling.
- Assumes standard atmospheric conditions for altitude-to-pressure conversion.
- Antoine constants are most reliable over common temperature ranges near water boiling conditions.
- Local weather systems can slightly raise or lower actual pressure and boiling point.
FAQ
Does water always boil at 100°C?
No. It boils at 100°C only at 1 atm pressure (sea-level standard pressure).
Why does pasta cook differently in the mountains?
Because water boils at a lower temperature, so the cooking water is less hot than at sea level.
Can I increase boiling temperature at home?
Yes. A pressure cooker increases pressure, which increases boiling temperature.