Temperature, Dewpoint, and Relative Humidity Calculator

Do you want to calculate relative humidity, dew point, or air temperature? You've come to the right place! Our online humidity and dew point calculator can determine the estimated water vapor and dew level in your environment. We'll also explain how dew point and indoor temperature affect humidity and teach you how to calculate relative humidity with just a few formulas.

Dew Point, Temperature, and Relative Humidity Calculator 

  • Fahrenheit (ºF) / Celsius (ºC)
  • Temperature — T (°)
  • Dew point — Td (°)
  • Relative Humidity — RH (%)


Please fill in any 2 of the below fields and click "Calculate". The resulted value will appear in the blank field.

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How to Use an Online Calculator for Humidity and Dew Point

Our relative humidity, air temperature, and dew point calculator can help you determine the optimal values for your environment. Here's how to use it:

  1. Choose the type of temperature scale (Fahrenheit: ºF; Celsius: ºC).

  2. Enter the values for dew point (Td) and relative humidity (RH).

  3. Press “Calculate” to get an estimate of the needed value.

Sound complicated? Let's break down the basics.

What Is Humidity (Relative, Absolute, and Specific)?

What Is Humidity

Humidity is the amount of water vapor held in the air. Higher levels of water content in the air result in fog and precipitation. More importantly, high humidity levels may cause condensation and the formation of mildew that can impact human respiratory systems or damage physical objects. That's why knowing how to calculate humidity is critical for libraries, museums, archives, and healthcare facilities.

Temperature is crucial for indoor humidity and air quality. Warm air can handle more moisture than cooler air. For instance, water is likely to condense if the indoor air is colder compared to the outdoor temperature. Conversely, the air becomes drier if your air conditioner heats your room while it's freezing outside.

Humidity and temperature calculators work based on absolute, relative, and specific humidity. Let's look at each type:

  • Absolute humidity. Absolute humidity refers to the exact amount of water vapor in the air, regardless of the current temperature. This metric is measured in grams of vapor per cubic meter of air volume.

  • Specific humidity. Specific humidity shows how many grams of water vapor are contained in a kilogram of air.

  • Relative humidity. This value shows how much water is in the air compared to the maximum water vapor it can hold at a specific temperature. Relative humidity can also be expressed as the ratio of vapor pressure to saturated vapor pressure. The relative humidity is expressed in the percentage of the water (relative to the air temperature).

Relative humidity (RH) is the most useful humidity indicator for air saturation. Meteorologists rely on relative humidity to forecast weather (like frost, precipitation, fog, and other conditions).

Indoor dew and mildew can form based on your indoor level of relative humidity. For instance, 50% relative humidity means the air needs 2x more water to be saturated. Super low levels of moisture lead to coughing, eye irritation, and respiratory issues. On the other hand, 100% relative humidity can cause dew and mold. 

Professionals use hygrometers to measure relative humidity values. On top of that, you can learn how to calculate relative humidity with temperature and dew point by reading below.

How to Measure Relative Humidity

To measure relative humidity, a variety of tools known as hygrometers can be used. A psychrometer works by measuring the difference between dry bulb temperature and wet bulb temperature. Hair hygrometers measure the relationship between the relative humidity and length of hair. Capacitive-type electronic hygrometers detect changes in a sensor's capacitance when it absorbs moisture. And finally, chilled-mirror dew point hygrometers measure the dew point temperature for calculating relative humidity.

What Is the Ideal Level of Indoors Humidity?

It's usually 30-50% humidity that we all find the most comfortable. Lower saturation levels can cause great discomfort and even itching, due to the extremely dry air.

If the air is saturated with higher than 50% humidity, it will make the air feel hotter than it actually is. High humidity also leads to the growth of mold and can cause severe health problems. To better understand how to control indoor air quality, read our humidity control tips article.

What Is a Dew Point?

what is dew point


The dew point means the temperature the air requires to achieve 100% of relative humidity (RH). At this level of air saturation, water will condense and transform into a liquid form, resulting in dew formation. 

The dew point correlates with the amount of water content in the air. Humidity causes the dew point to rise, and 100% relative humidity means the dew point equals the temperature.

In other words, dew points refer to the point where the air can't hold any more water vapor. So, when the air temperature gets cooler, the gaseous water turns into liquid. This means, when the temp goes up, the relative humidity decreases, and vice versa.

Now, why should you know about the dew point and air temperature calculation? Dew itself isn't dangerous, as it's basically condensed water. You often see dew on grass or flowers after a foggy day. 

However, dew often leads to mold and wet bulbs in your home, which can impact your comfort and health. Lower dew point means the indoor humidity prevents your body from evaporating sweat, making it more difficult for you to cool down. This can make your skin irritate or dry your airways.

Looking at the relative humidity is not enough to improve indoor air quality. You need to maintain the right level of relative humidity and indoor temperatures in relation to the dew point. 

You can determine your dew point value with special devices called dew point meters. If you don't have access to this equipment, using an online RH calculator would be the easiest way. Alternatively, you can calculate the dew point from RH and temp values using the formulas below.

How to Calculate Relative Humidity and Dew Point?

dew point temperature

Relative humidity, dew point, and temperature are related to one another. You can easily calculate the dew point from relative humidity and temperature. However, determining the relative humidity requires additional data. 

Relative Humidity Calculation Formula

There's more than one way to calculate relative humidity. Here are some formulas you can use:

  • Equation 1: RH = E/Es × 100

In this equation, RH means relative humidity, E is the amount of water vapor, and Es refers to the amount of water content that would be in the air with an equal temperature and pressure level.

  • Equation 2: RH = 100 × E × ( (243.04 × 17.625 (Td−T) ) / ( (17.625 + T) × (17.625 +Td) )

Td refers to the dew point, and T refers to air temperature in this equation. 

  • Equation 3: RH = 100% × AH × AHmax

Here, AH means absolute humidity, and AHmax is the maximum level of absolute humidity.

Absolute Humidity Calculation Formula

You can also calculate absolute humidity from relative humidity and temperature.

  • Equation: AH = ( 6.112 × E^ × [(17.67 × T) / (T + 243.5)] × RH × 2.1674 ) / ((273.15 + T)

As before, T means temperature, and RH stands for relative humidity. The E^ equals 2.71828.

Dew Point Calculation Formula

It's easy to calculate the dew point if you know the relative humidity and temperature.

  • Equation: Td = T - ( (100 - RH)/5)

In this equation, Td is the dew point, and RH means relative humidity.

Important note: the results will be in Celsius. To calculate the dew point in Fahrenheit, use the following formula:

ºF = ( °C × 9/5 ) + 32

However, you can always use our dew point temperature calculator, which shows results in Fahrenheit and Celsius.


You should know your humidity level and dew point to maintain your indoor air quality. Thankfully, you can easily determine these values using our DP and relative humidity calculator. We also hope our formulas have taught you how to calculate dew point with temperature and humidity (and vice versa) by yourself.

Do you want to ensure the best possible air quality in your home or office? Take a look at our selection of HVAC products that help you improve your space's air quality! And don't hesitate to contact Blackhawk Supply if you haven't found what you are looking for!

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