Home › Weather & Environment › Boiling Point at Altitude Calculator

Boiling Point at Altitude Calculator

Computes the boiling point of water at a given altitude by taking the ISA pressure at that altitude (or a measured station pressure) and solving the Antoine equation for water, with a note on cooking at altitude.

When to use

You need the boiling temperature of water at your elevation for cooking, canning, brewing, candy making or laboratory work, or the boiling point at a measured barometric pressure.

Do not use when: You need the boiling point of a liquid other than water or of salt/sugar solutions (boiling-point elevation), or altitudes above 9000 m.

Formula

p = 1013.25 × (1 − 0.0065·h/288.15)^5.25578 hPa (ISA); P_mmHg = p / 1.333224; T_boil = 1730.63 / (8.07131 − log10(P_mmHg)) − 233.426 °C (Antoine equation for water, valid 1–100 °C)

The standard atmosphere is an average; on a given day the real pressure, and hence the boiling point, varies by about ±0.5 °C with weather. Rule of thumb: the boiling point falls about 1 °C per 300 m (1 °F per 500 ft).

Inputs

Parameter	Type	Unit	Required	Description
`altitude`	number		yes	Elevation above sea level in altitude_unit (−500 to 9000 m). Range: ≥ -1640, ≤ 29500
`altitude_unit`	enum: m \| ft		default m	Unit of the altitude input.
`pressure_hpa`	number	hPa	no	Actual absolute pressure at the site in hPa; when given it replaces the standard-atmosphere pressure for the altitude. Range: ≥ 200, ≤ 1100

Outputs

Output	Type	Unit	Description
`boiling_point_c`	number	°C	Boiling temperature of pure water at the site pressure.
`boiling_point_f`	number	°F	Boiling point in Fahrenheit.
`boiling_point_drop_c`	number	°C	100 °C minus the local boiling point.
`pressure_hpa`	number	hPa	Standard-atmosphere pressure at the altitude, or the measured pressure if supplied.
`pressure_mmhg`	number	mmHg	Same pressure in millimetres of mercury.
`altitude_m`	number	m	Altitude in metres.
`altitude_ft`	number	ft	Altitude in feet.
`cooking_note`	string		Practical consequence for boiling and simmering food at this altitude.

Example

1500 m: {"altitude":1500,"altitude_unit":"m"} → {"boiling_point_c":95,"boiling_point_f":203,"boiling_point_drop_c":5,"pressure_hpa":845.6,"pressure_mmhg":634.2,"altitude_ft":4921}

Denver, 5280 ft: {"altitude":5280,"altitude_unit":"ft"} → {"boiling_point_c":94.7,"boiling_point_f":202.4,"altitude_m":1609,"pressure_hpa":834.3}

GET https://tttkmbb.com/api/v1/calculate/boiling-point-altitude?altitude=1500&altitude_unit=m

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/boiling-point-altitude (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/boiling-point-altitude · Markdown: https://tttkmbb.com/weather/boiling-point-altitude.md · JSON definition: https://tttkmbb.com/weather/boiling-point-altitude.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="boiling-point-altitude"
OpenAPI operationId: calculate_boiling_point_at_altitude
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Wikipedia – Antoine equation (water coefficients, 1–100 °C) (reference)
Wikipedia – International Standard Atmosphere (ICAO Doc 7488) (reference)
Wikipedia – High-altitude cooking (boiling point table) (reference)

FAQ

Why does food take longer to cook at altitude?

Boiling water is cooler, so heat transfers into the food more slowly; pasta, rice, beans and eggs need more time and often more liquid, and some foods never soften without a pressure cooker.

Does adding salt raise the boiling point noticeably?

Barely: a typical 1 % kitchen brine raises it by about 0.2 °C, far less than the drop from a few hundred metres of elevation.

Which pressure should I enter?

The absolute (station) pressure read at the site, not the sea-level-corrected value from weather reports; leave it empty to use the standard atmosphere.

Related calculators

Pressure Altitude Calculator — Standard pressure at an altitude and station pressure from QNH.
Turkey Cooking Time Calculator — Roasting times also change with altitude and oven temperature.
Temperature Converter — Convert the boiling point between °C and °F.