Dew Point Calculator

About Dew Point Calculator

Dew point is the temperature at which water vapor condenses. Higher dew point = more humid. Above 20°C feels oppressive.

How to use this calculator

1. Enter the air temperature.
2. Enter the relative humidity.
3. Calculate the dew point using the formula.

The formula explained

• \(\text{dew point}\) = the temperature at which air reaches saturation and water vapor starts to condense
• \(T\) = air temperature
• \(\text{RH}\) = relative humidity in percent

Step by step method

1. Start with the current air temperature and relative humidity.
2. Subtract the relative humidity from 100 to find the humidity gap.
3. Divide that gap by 5, then subtract the result from the air temperature.
4. The final number is the estimated dew point temperature.

Worked example

Suppose the air temperature is 30 degrees and the relative humidity is 70 percent.

1. Compute the humidity gap: \(100 - 70 = 30\).
2. Divide by 5: \(30 \div 5 = 6\).
3. Subtract from the air temperature: \(30 - 6 = 24\).

Tips and common mistakes

• Make sure relative humidity is entered as a percent, not as a decimal.
• Use the same temperature unit throughout, since the calculator returns the dew point in that unit.
• This is an estimate, so small differences from other dew point methods are normal.
• Higher dew point values usually mean air feels more humid.

Frequently asked questions