Last updated: July 3, 2026
Boiling Point at Altitude Calculator
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Quick Answer
The boiling point at altitude calculator estimates water's boiling point using Tb(°C) ≈ 100 − altitude_m/285. Enter altitude in metres or feet to get boiling point in °C and °F plus estimated atmospheric pressure in kPa and atm.
Water boils at a lower temperature at higher altitude because atmospheric pressure is lower. A useful estimate is boiling point in Celsius equals 100 minus altitude in metres divided by 285.
Key Takeaways
- Water boils when its vapour pressure equals surrounding atmospheric pressure.
- The calculator uses Tb(°C) ≈ 100 − altitude_m/285 as the primary engineering approximation.
- At 1500 m, the model gives about 94.7 °C; at 2850 m, it gives about 90 °C.
- The pressure output is estimated with the standard-atmosphere barometric formula.
- Weather, dissolved solutes, and sealed vessels can make real boiling points differ from this open-water estimate.
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Formula
Tb(°C) ≈ 100 − altitude_m / 285; P = 101325 × (1 − 2.25577e−5 h)^5.25588 Pa
Where:
- T_b=Estimated boiling point of water(°C)
- h=Altitude above sea level(m)
- P=Estimated atmospheric pressure(Pa or kPa)
Worked Examples
Sea level kitchen
At approximately 0 m altitude, the familiar normal boiling point applies.
- 1Use Tb ≈ 100 − h/285.
- 2Substitute h = 0 m: Tb = 100 − 0/285 = 100 °C.
- 3Convert to Fahrenheit: 100 × 9/5 + 32 = 212 °F.
Mountain town at 1500 m
A moderate mountain elevation noticeably lowers water's boiling point.
- 1Use the linear approximation Tb ≈ 100 − altitude_m/285.
- 2Substitute 1500 m: Tb = 100 − 1500/285 = 94.74 °C.
- 3The calculator also estimates pressure from the barometric formula, about 84.6 kPa.
High-altitude camp at 2850 m
At high elevation, water boils about ten degrees Celsius cooler than at sea level.
- 1Compute Tb = 100 − 2850/285.
- 2Tb = 100 − 10 = 90 °C.
- 3Convert to Fahrenheit: 90 × 9/5 + 32 = 194 °F.
Introduction
Water boils when its vapour pressure equals the surrounding pressure. Because atmospheric pressure falls with altitude, the boiling point of water also falls: pasta, rice, sterilization, and laboratory reflux all run cooler on a mountain than at sea level. This calculator uses the practical engineering rule Tb(°C) ≈ 100 − altitude_m/285 as the primary output and also reports pressure from a standard-atmosphere barometric estimate. For related pressure work, compare the partial pressure calculator or solution boiling changes with the boiling point calculator. Background definitions are consistent with NIST water property data and standard-atmosphere references from NOAA.
Why altitude changes boiling point
Boiling begins when water vapour bubbles can grow against the pressure pushing on the liquid. At sea level that pressure is about 101.325 kPa, so pure water boils near 100 °C. At higher altitude the air column above you is smaller, pressure is lower, and bubbles form at a lower temperature. Below sea level, higher pressure raises the boiling point slightly.
Higher altitude means lower atmospheric pressure.
Lower pressure means water boils at a lower temperature.
The change affects cooking time because boiling water is cooler.
The result is an estimate for pure water in an open vessel.
Boiling point at altitude formula
The primary calculator output uses Tb(°C) ≈ 100 − h/285, where h is altitude in metres. This is a compact engineering approximation near ordinary inhabited elevations. It is equivalent to roughly −1 °C for every 285 m, or about −1.8 °F for each 935 ft. The pressure shown is calculated independently with P = 101325(1 − 2.25577×10⁻⁵h)^5.25588 Pa.
The linear rule is deliberately simple; for high-precision thermodynamics use tabulated saturation-pressure data or a full Antoine/Clausius–Clapeyron model.
How to calculate boiling point from altitude
Enter an altitude and choose metres or feet. The calculator converts feet to metres, subtracts h/285 from 100 °C, converts the result to °F, and then estimates atmospheric pressure. The workflow is easy to check by hand for round values.
- Convert altitude to metres if needed:
h_m = h_ft / 3.28084.
- Calculate Tb in Celsius:
100 − h_m/285.
- Convert to Fahrenheit:
°F = °C × 9/5 + 32.
Use pressure as a context value, not the primary boiling-point model.
Common altitude reference values
These approximate values help sanity-check the result. Weather, water purity, and local pressure systems can move actual boiling temperature by a small amount.
| Location or altitude | Approx. pressure | Estimated boiling point |
|---|---|---|
| Sea level, 0 m | 101.3 kPa | 100.0 °C |
| 1500 m | 84.6 kPa | 94.7 °C |
| 2850 m | 72.0 kPa | 90.0 °C |
| Denver, about 1609 m | ≈ 83 kPa | ≈ 94.4 °C |
| Mount Everest summit, 8849 m | ≈ 31 kPa | ≈ 69.0 °C |
Cooking and laboratory implications
At altitude, boiling water is cooler even though it may look vigorous. Food often needs more time because heat transfer happens at a lower maximum liquid temperature. In the lab, open-vessel boiling, reflux temperatures, water baths, and simple distillation may shift. If solutes are important, combine this altitude estimate with concentration tools such as the molarity calculator and colligative-property ideas from the osmotic pressure calculator.
Pressure cookers counteract altitude by increasing pressure, which raises water's boiling temperature.
Assumptions and limitations
This calculator is an educational and engineering estimator for pure water in an open container. It does not model weather-driven pressure variation, humidity, dissolved salts, non-water solvents, sealed vessels, or the exact curvature of the water vapour-pressure curve. For authoritative thermodynamic work, consult standards such as the IAPWS releases or NIST data.
Best for approximate cooking, field, and classroom calculations.
Actual local pressure can differ from the standard atmosphere.
Dissolved solutes can raise boiling point while altitude lowers it.
Use a calibrated thermometer and barometer for experimental validation.
Quick Reference Card
Boiling Point at Altitude — Quick Reference
Quick reference • Boiling Point at Altitude Calculator
Tb(°C) ≈ 100 − altitude_m / 285Valid range: Best as a practical estimate from about −500 m to 9000 m for pure water in an open vessel
Common Values
⚠ Watch Out
- •This is an approximation, not a substitute for measured local pressure.
- •Use pure-water assumptions only; dissolved solutes change boiling point.
- •Weather systems can shift actual atmospheric pressure and boiling temperature.
- •Do not use open-boiling estimates for sealed pressure vessels or autoclaves.
Pro Tips
- →For feet, the calculator converts altitude to metres before applying the formula.
- →Use a pressure cooker to raise water temperature at altitude.
- →For lab reflux, record actual barometric pressure when precision matters.
- →Check both °C and °F outputs when following cooking instructions from another region.
FAQs
What formula does this boiling point at altitude calculator use?
It uses the linear estimate Tb(°C) ≈ 100 − altitude_m/285 for the primary boiling point, then converts the result to °F and estimates pressure with the barometric formula.
Why does water boil at a lower temperature on mountains?
Atmospheric pressure decreases with altitude. Since boiling occurs when water vapour pressure equals external pressure, less external pressure lets water boil at a lower temperature.
Is the pressure output used to calculate the boiling point?
No. The primary boiling-point output follows the requested linear engineering approximation. Pressure is reported alongside it for context and sanity checking.
Can I enter altitude in feet?
Yes. Choose feet in the unit selector and the calculator converts the value to metres before applying the boiling-point formula.
Does salt water behave the same way?
No. Dissolved solutes raise boiling point, while altitude lowers it. For salty or sugary solutions, the net temperature depends on both pressure and boiling-point elevation.
Why does food take longer to cook at altitude?
Boiling water is cooler at altitude, so food cooked in boiling water receives heat at a lower temperature. More time or a pressure cooker may be needed.