Boiling Point at Altitude Calculator
The temperature water boils at for your altitude or air pressure, and how much lower that is than at sea level.
Result
Boiling point of water: 202.4 °FEstimate
Uses the standard atmosphere’s pressure for the altitude. The weather moves the real pressure, and the boiling point with it; a barometer reading taken where you are is closer.
- Air pressure
- 24.64 inHg (83.43 kPa)Estimate
- Lower than at standard sea-level pressure by
- 9.6 °F (5.4 °C)Estimate
https://calcgallery.com/chemistry/boiling-point-altitude-calculator/
Results come from the published equations applied to the values you enter. They are not electrical design, conductor sizing, laboratory safety or medical guidance. Weather indices describe a standard person in standard conditions and are not a forecast. Where codes apply, local rules vary and must be checked. Read the full disclaimer
How to use the Boiling Point at Altitude Calculator
- Enter your altitude above sea level, or switch to a pressure and type the reading from a barometer where you are.
- Read the temperature water boils at, the air pressure the page used, and how much lower that is than at sea level.
The formulas
geopotential height H = r₀ × Z ÷ (r₀ + Z) r₀ = 6,356,766 mair pressure P = 101,325 Pa × (1 − 0.0065 × H ÷ 288.15)^5.2559boiling point T = 1663.125 ÷ (5.08354 − log₁₀ P) + 45.622Z is your altitude in metres, P is in bar in the last line and T comes out in kelvin. The exponent 5.2559 is g₀M₀ ÷ (R*L) from the standard’s own constants.
Cooking at altitude
Because water cannot get hotter than its boiling point in an open pot, anything simmered or boiled cooks more slowly at altitude. Recipe adjustments depend on the food and are not covered here; follow a tested high-altitude recipe or the guidance of your local food safety authority.
What the diagram shows
The boiling point of water against altitude from sea level up, with your altitude marked on the curve and your boiling point as a dashed line.
With your numbers
- Standard-atmosphere pressure at that altitude = 83,431.8 Pa
- T = 1663.125 ÷ (5.08354 − log₁₀(0.834318 bar)) + 45.622 = 367.795 K = 94.65 °C
Quick reference
Uses the standard atmosphere’s pressure for the altitude. The weather moves the real pressure, and the boiling point with it; a barometer reading taken where you are is closer.
| Example | Boiling point of water |
|---|---|
| Sea level | 100 °C |
| 1,000 m | 96.7 °C |
| 5,280 ft (Denver) | 202.4 °F |
| 10,000 ft | 193.7 °F |
| 3,000 m | 90 °C |
| 8,849 m (Everest) | 70.2 °C |
| Barometer reading 84 kPa | 94.8 °C |
Where the numbers come from
The fixed figures this calculator relies on, and the published source each one was checked against. How the calculators are built and checked
7 sources
U.S. Standard Atmosphere, 1976 (NOAA-S/T 76-1562), Table 2, P₀ = 1.013250 × 10^5 N/m² (or Pa). https://www.ngdc.noaa.gov/stp/space-weather/online-publications/miscellaneous/us-standard-atmosphere-1976/us-standard-atmosphere_st76-1562_noaa.pdf
Used for
- Standard sea-level atmospheric pressure P₀ of the standard atmosphere.
U.S. Standard Atmosphere, 1976, Table 2 and p. 4: T₀ = 288.15 K.
Used for
- Standard sea-level temperature T₀, 15 °C.
U.S. Standard Atmosphere, 1976, Table 4: L(M,0) = −6.5 K/km′ from H₀ = 0 to H₁ = 11 km′.
Used for
- The fall in temperature with height in the lowest layer of the standard atmosphere, 0 to 11 geopotential kilometres.
U.S. Standard Atmosphere, 1976, p. 9, section 1.2.4: M₀ = 28.9644 kg/kmol.
Used for
- Mean molar mass of sea-level dry air M₀ in the standard atmosphere.
U.S. Standard Atmosphere, 1976, Table 2 and p. 3: R* = 8.31432 × 10^3 N·m/(kmol·K).
Used for
- The gas constant R* the standard atmosphere is defined with. Not the 2019 SI value; the Standard says it is not exactly consistent with k and N_A.
U.S. Standard Atmosphere, 1976, Table 2 and p. 3: g₀ = 9.80665 m/s².
Used for
- Standard acceleration of gravity g₀, the value adopted by the CIPM in 1901.
U.S. Standard Atmosphere, 1976, Table 2 and p. 4: r₀ = 6356.766 km.
Used for
- Effective earth radius r₀ used to convert geometric altitude to geopotential altitude.
Common questions about the Boiling Point at Altitude Calculator
- Why does water boil at a lower temperature at altitude?
- Water boils when its vapour pressure reaches the pressure of the air above it. Higher up there is less air overhead, so the pressure is lower and the water reaches it at a lower temperature. At 5,280 ft the standard atmosphere’s pressure is about 83.4 kPa and water boils near 94.6 °C (202 °F).
- How accurate is the answer?
- The page uses the standard atmosphere, an agreed average; on any real day the weather moves the air pressure up or down, and the boiling point with it. For a better figure, enter the pressure from a barometer at your location. Use the station pressure, not the sea-level-adjusted value weather reports give, which is corrected back to sea level and would put you at the coast.
- Where do the numbers come from?
- The pressure at each altitude follows the U.S. Standard Atmosphere, 1976, which defines sea-level pressure as 101,325 Pa and a temperature falling 6.5 °C per kilometre. The boiling point comes from the Antoine equation for water with coefficients the NIST Chemistry WebBook lists, fitted over 344 to 373 K, about 71 °C to 100 °C.
- Does salt or sugar change this?
- Yes, both raise the boiling point a little, and more as the solution gets stronger. This page is for pure water only.
- What about very high altitudes?
- The page covers the first layer of the standard atmosphere, up to 11 km. Near the top of Everest the boiling point drops below 71 °C, the bottom of the range the Antoine coefficients were fitted over; the page still answers and says it is an extrapolation.