Boiling Point Calculator
Use this boiling point calculator to estimate how the boiling temperature of a liquid shifts when the surrounding pressure changes.
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Run the calculator.
What This Boiling Point Calculator Helps You Do
This page helps you estimate how a liquid's boiling temperature changes when pressure changes, which is the most practical use case behind the Omni reference. It is useful for altitude cooking checks, vacuum evaporation estimates, and quick process design sanity checks.
The result panel reports both Kelvin and Celsius so you can move from the thermodynamics equation to a practical temperature target without doing another conversion by hand.
How to Calculate Boiling Point Calculator
- Enter a known boiling point: Provide the liquid's boiling point at a known pressure.
- Use consistent pressure units: The calculator converts atm, kPa, and mmHg internally, so the reference and target pressures stay comparable.
- Supply dHvap: Enter the enthalpy of vaporization for the liquid in kJ/mol.
- Interpret the shift: Lower pressure lowers the boiling point, while higher pressure raises it.
Boiling Point Calculator Formula
| Variable | Meaning | Unit |
|---|---|---|
| P1 | Reference pressure | atm, kPa, or mmHg |
| P2 | Target pressure | atm, kPa, or mmHg |
| T1 | Reference boiling point | K |
| T2 | Target boiling point | K |
| dHvap | Molar enthalpy of vaporization | kJ/mol |
| R | Gas constant | 8.314 J/mol-K |
Use the worked examples below to check how the formula behaves with real values. If the result looks unexpected, verify the unit assumptions and the meaning of each variable before interpreting the answer.
Worked Examples
- Liquid: Water
- T1: 100 deg C
- P1: 1 atm
- P2: 0.8 atm
- dHvap: 40.65 kJ/mol
Result: T2 is about 93.75 deg C.
Water boils sooner as ambient pressure drops.
- Liquid: Water
- T1: 100 deg C
- P1: 1 atm
- P2: 2 atm
- dHvap: 40.65 kJ/mol
Result: T2 is about 120.84 deg C.
Pressurized systems raise the boiling point substantially.
- Liquid: Water
- T1: 100 deg C
- P1: 1 atm
- P2: 0.5 atm
- dHvap: 40.65 kJ/mol
Result: T2 is about 81.25 deg C.
Vacuum evaporation works because the boiling point drops quickly.
- Liquid: Ethanol
- T1: 78.37 deg C
- P1: 1 atm
- P2: 0.7 atm
- dHvap: 38.56 kJ/mol
Result: T2 is about 69.12 deg C.
Different liquids respond differently because dHvap changes from one substance to another.
How to Interpret Your Results
| Range | Meaning | Action |
|---|---|---|
| Target pressure below reference | The liquid boils at a lower temperature. | Expect faster boiling or evaporation under reduced pressure. |
| Target pressure above reference | The liquid needs more heat before boiling. | Check whether the vessel is pressurized and whether the material remains stable. |
| Large pressure change | Small dHvap errors create bigger temperature differences. | Use substance-specific data rather than a rough estimate. |
Frequently Asked Questions
References
Last reviewed: March 2026