With our boiling point calculator, you can quickly determine the atmospheric boiling point of various substances. You may also calculate the boiling point at different pressures.

Wondering what's the boiling point of water or other substances? or maybe you're not sure if there's any change in the boiling point of water for different pressures? 🤔 Then you may find this tool useful.

If you'd like to find out about these, we invite you to keep on reading the accompanying and also learn:

  • The boiling point definition;
  • How does pressure affect the boiling point;
  • The boiling point formula.

You might also be interested in other processes involving liquids. If so, then you should visit our dissociation equation calculator!

What is boiling point? – Boiling point definition

We're all familiar with the process of boiling water in a pot. We fill the pot with water, place it on the stove, and wait for it to heat up. After a while, we'll notice bubbles forming in the hot water, indicating that the water is boiling. Do you know at what temperature this happens?

It's common to hear that water boils at 100°C. But if we'd like to be more precise, we should say that water boils at 100°C when it's at atmospheric pressure. Why do we need to specify both temperature and pressure? It turns out that depending on the pressure, water or any other liquid has different boiling points.

The boiling point is the temperature at which a liquid substance changes to its gaseous phase. This happens when the vapor pressure of a liquid equals the surrounding pressure. Whenever a liquid is heated, and this pressure balance takes place, it turns into vapor.

Notice from this boiling point definition that if the surrounding pressure varies, so does the vapor pressure. That is, the boiling point varies with pressure. The higher the pressure, the higher the boiling point, and vice versa. Water boils at 100 °C (212 °F) at sea level (0 m), where pressure is higher. However, at higher altitudes, hence lower pressures, like 2000 m above sea level, water boils at 98 °C (208.4 °F).

💡 Did you know that boiling point is also affected by the amount of solute added to a solvent? As a result, the boiling point of the liquid increases. This is known as boiling point elevation.

How to calculate boiling point – Clausius-Clapeyron equation

By means of the Clausius-Clapeyron equation, we can observe how pressure affects the boiling point. This equation characterizes phase changes such as vaporization or sublimation by relating temperature, pressure, and heat of vaporization (or enthalpy of sublimation).

With the Clausius-Clapeyron equation is possible to determine the boiling point of any substance at a given pressure. Let's take a closer look:

ln(P1P2)=ΔHR ×(1T11T2)\small ln\left(\cfrac{P_1}{P_2}\right) = \cfrac{-\Delta H}{R} \ \times \left(\cfrac{1}{T_1} - \cfrac{1}{T_2}\right)

where:

  • P1P_1 — Pressure at state 1;
  • P2P_2 — Pressure at state 2;
  • T1T_1 — Boiling point at state 1 (at pressure equal to P₁);
  • T2T_2 — Boiling point at state 2 (at pressure equal to P₂);
  • ΔH\Delta H — Latent heat of vaporization of the substance, measured in J/mol; and
  • RR — Ideal gas constant, equal to 8.314 J/(K⋅mol).

Let's see how to calculate the boiling point temperature with this formula. Simply substitute the known values, P1P_1, P2P_2, ΔH\Delta H, RR, and T1T_1. Then proceed to clear the boiling temperature at the sate 2, T2T_2.

Would you like to continue exploring phase changes in water? Why not take a look at our dew point calculator and learn how relative humidity affects water going from vapor to condensate?

How to use the boiling point calculator

Use the boiling point calculator to find the boiling point at a given pressure for different substances such as water, hydrogen, methane, or others. To make use of this tool:

  1. Select the substance that you're interested in studying. For this, click on the drop-down menu associated with the Substance field.
  2. In the section below, State 1 (The normal boiling point), the calculator will show the boiling temperature of the substance at the atmospheric pressure (1 atm or 1013.25 hPa).
  3. Finally, in the State 2 section, you'll be able to find the boiling point of the substance at any other pressure. For this, simply input the desired pressure, and the calculator will indicate the temperature.

🙋 By clicking on the Advanced mode button, the calculator will display the heat of vaporization of your substance.

Gabriela Diaz
Substance
Water
State 1 (The normal boiling point)
Pressure
1.01325
bar
Boiling point
212
°F
State 2
Pressure
bar
Boiling point
°F
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