Boiling Point Calculator
Enter the ambient pressure and choose a unit to find the temperature at which pure water boils. The calculator uses the IAPWS-IF97 saturation equation, valid from about 0.611 kPa to 22,064 kPa.
Last updated: September 26, 2026
Frequently asked questions
How does pressure affect the boiling point?
Water boils when its vapor pressure equals the surrounding pressure. Lower pressure means a lower boiling temperature, and higher pressure raises it.
Is the boiling point of water at 1 atm exactly 100 °C?
On the current temperature scale (ITS-90) it is about 99.97 °C at 101.325 kPa. The round 100 °C figure comes from the older definition of the Celsius scale.
Should I enter absolute or gauge pressure?
Absolute. A gauge reading is relative to atmospheric pressure, so add the ambient pressure to convert it before entering it here.
Does this work for liquids other than water?
No. It is a water-specific correlation. Other liquids have different vapor-pressure curves, and this calculator does not include them.
How is this different from the altitude and elevation calculators?
This one starts from pressure. The Boiling Point at Altitude calculator starts from elevation, and the Boiling Point Elevation calculator starts from a dissolved solute.
What is the valid range?
About 0.611 kPa to 22,064 kPa, that is, from the triple point to the critical point of water. Outside that range the calculator asks for another value.