How do I calculate the dew point?

The dew point is calculated using ambient temperature (T) and relative humidity (RH). The standard scientific approach uses the Magnus-Tetens approximation formula: gamma(T, RH) = (17.625 * T) / (243.04 + T) + ln(RH/100). The dew point Tdp = (243.04 * gamma) / (17.625 - gamma).

What's worse, humidity or dew point?

Dew point is a better absolute indicator of comfort than relative humidity. Relative humidity depends on temperature (warm air holds more moisture than cold air). The dew point represents the actual volume of water vapor in the atmosphere. A high dew point (e.g. above 65°F / 18°C) always feels sticky and humid, regardless of relative humidity percentage.

At what dewpoint does it start to feel uncomfortable?

Uncomfortability begins when the dew point exceeds 60°F (15.5°C), which starts to feel muggy. Dew points above 65°F (18.3°C) are considered sticky and uncomfortable, while dew points above 70°F (21°C) feel oppressive and sticky.

How to convert dew point to ppm?

Converting dew point to parts per million (ppm) requires knowing the system pressure. Under atmospheric pressure (1 bar), a dew point temperature corresponds to a specific water vapor pressure. You can calculate this vapor pressure using Arden Buck equations and divide it by the total pressure to find the ratio in ppm.

Dew Point Calculator

Determine the exact temperature at which air reaches saturation and dew begins to condense, indicating comfort levels.

Atmospheric Inputs

Dew Point Index

Calculated Dew Point

16.7°C

Comfortable environment.

Dew Point Comfort Chart

Below 10°C (50°F): Very dry, fresh and pleasant.
10°C to 15°C (50-59°F): Comfortable, standard summer air.
16°C to 20°C (60-68°F): Noticeably humid, sticky.
Above 20°C (68°F): Oppressive, extremely sticky and muggy.

Dew Point Condensation, Evaporative Comfort & Saturation Physics

Calculate the dew point condensation temperature. Learn how relative humidity index maps to comfort scales and mold prevention.

Frequently Asked Questions

It is the temperature at which air becomes fully saturated with moisture, causing water vapor to condense into dew or fog.

Dew point is an absolute measure of air moisture. Relative humidity changes with air temperature, making it a deceptive indicator of how humid the air actually feels.

It is an empirical formula used to calculate dew point: Td = (b * alpha) / (a - alpha), where alpha is a function of temperature and relative humidity.

Mold thrives when the relative humidity at surfaces exceeds 70%, which typically occurs when indoor dew points rise above 16°C (60°F). Keep indoor dew points below 13°C (55°F).

High dew points inhibit sweat evaporation, leading to rapid increases in core body temperature, dehydration, muscle cramps, and heat exhaustion.

The dew point applies when condensation occurs as liquid water. If the saturation temperature falls below 0°C (32°F), it is called the frost point, as water vapor transitions directly into ice crystals.