Dew Point Calculator

Calculate dew point from temperature and humidity

Dew Point Calculator

Calculate the dew point temperature based on current air temperature and relative humidity. The dew point tells you when moisture will condense out of the air, helping you understand comfort levels, fog risk, and atmospheric conditions.

Input Values

°F
%

Results

Dew Point Temperature
--
Temperature at which air becomes saturated
Temperature Spread
--
Difference between air temp and dew point
Fog Risk

Low spread indicates high fog or condensation risk. Visibility may be reduced.

Frost Point Conditions

Dew point is below freezing. Frost may form instead of dew.

Comfort Level
--
Enter values above
Temperature and humidity required

Dew Point Comfort Reference

< 50°F (10°C)
Dry
Feels pleasant and crisp
50-59°F (10-15°C)
Comfortable
Ideal outdoor conditions
60-64°F (16-18°C)
Sticky
Slightly muggy, noticeable moisture
65-69°F (18-21°C)
Uncomfortable
Humid and uncomfortable for most
70-74°F (21-23°C)
Oppressive
Very humid, difficult to cool down
75°F+ (24°C+)
Miserable
Extremely humid, tropical conditions

About Dew Point

The dew point is the temperature at which air becomes saturated with moisture and water vapor begins to condense into liquid water (dew). Unlike relative humidity, which changes with temperature, the dew point is an absolute measure of moisture in the air.

A higher dew point means more moisture in the air, making it feel muggy and uncomfortable. A lower dew point indicates drier air, which feels more comfortable even at higher temperatures. Meteorologists and HVAC professionals use dew point as a more reliable indicator of comfort than relative humidity alone.

When the dew point is below freezing (32°F or 0°C), it becomes the frost point, meaning frost will form instead of dew. The temperature spread (difference between air temperature and dew point) indicates how close the air is to saturation. A spread less than 5°F suggests fog, mist, or condensation may form.

Frequently Asked Questions

What is dew point and why does it matter?
Dew point is the temperature at which air becomes saturated and water vapor condenses. It matters because it's a better indicator of comfort than relative humidity alone. A dew point above 65°F feels uncomfortable regardless of the actual temperature, while a dew point below 50°F feels pleasant and dry.
How is dew point different from humidity?
Relative humidity is a percentage that changes with temperature, while dew point is an absolute temperature that represents the actual amount of moisture in the air. For example, 50% humidity at 90°F contains far more moisture than 50% humidity at 50°F, but the dew point tells you exactly how much moisture is present.
What dew point is comfortable for humans?
Most people find dew points between 50-59°F (10-15°C) to be the most comfortable. Below 50°F feels dry and crisp, while above 60°F starts to feel sticky. Once the dew point exceeds 65°F, most people find the air uncomfortable and oppressive. Above 75°F is considered miserable and is typical of tropical climates.
What causes fog to form?
Fog forms when the air temperature drops to or near the dew point, causing water vapor to condense into tiny water droplets suspended in the air. When the spread between air temperature and dew point is less than 5°F, fog is likely to form, especially overnight when temperatures drop.
What is the frost point?
The frost point is the temperature at which water vapor in the air will condense directly into ice (frost) rather than liquid water (dew). This occurs when the dew point is below the freezing point of water (32°F or 0°C). Frost typically forms on surfaces overnight when the frost point is reached.
Can the dew point be higher than the air temperature?
No, the dew point cannot exceed the air temperature. When the air temperature equals the dew point, the air is 100% saturated (100% relative humidity), and condensation occurs. The dew point can approach the air temperature, but it cannot be higher under normal atmospheric conditions.
How accurate is the Magnus-Tetens formula?
The Magnus-Tetens formula used in this calculator is accurate to within 0.4°C for temperatures between -40°C and 50°C, which covers virtually all weather conditions humans experience. It's widely used in meteorology and HVAC applications because of its simplicity and reliability.

Privacy & Limitations

  • All calculations run entirely in your browser -- nothing is sent to any server.
  • Results are estimates and may vary based on actual conditions.

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Dew Point Calculator FAQ

What is Dew Point Calculator?

Dew Point Calculator is a free utility & everyday tool that helps you Calculate dew point from temperature and humidity with comfort level indicator.

How do I use Dew Point Calculator?

Enter your input values, review the calculated output, and adjust inputs until you reach the result you need. The result updates in your browser.

Is Dew Point Calculator private?

Yes. Calculations run locally in your browser. Inputs are not uploaded to a server by default, and refreshing the page clears session data.

Does Dew Point Calculator require an account or installation?

No. You can use this tool directly in your browser without sign-up or software installation.

How accurate are results from Dew Point Calculator?

This tool applies standard formulas or deterministic processing logic for estimates. For medical, legal, tax, or investment decisions, verify with a qualified professional.

Can I save or share outputs from Dew Point Calculator?

You can bookmark this page and copy outputs manually. Results are not persisted in your account and are typically not embedded in the URL.

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