Skip to content
QtywiseExplore tools ↗

Dew Point Calculator

Liquid-water dew-point approximation within a stated input range, distinct from wet-bulb temperature.

Created by:
Jamie C.
Jamie C.

Across her work, Jamie focuses on bridging operational precision with practical technology adoption. She develops industry-specific calculators, software guides, and technical content tailored to the construction, residential living, HVAC, and artificial intelligence sectors. By pairing hands-on systems design with advanced AI and automation workflows, her resources empower trade specialists, contractors, and growing teams to eliminate bottlenecks, forecast project requirements accurately, and run more efficient operations. Fluent in five languages, Jamie approaches every tool and article with an emphasis on clarity, actionable utility, and real-world results.

View profile
Published:

γ = ln(RH/100) + 17.67T/(243.5+T); dew point = 243.5γ/(17.67−γ).

Dew Point Calculation Formula (Magnus-Tetens Formula)

The Magnus-Tetens approximation formula computes dew point ($T_d$) from temperature ($T$ in °C) and relative humidity ($RH$ in %):

γ(T, RH) = (17.27 × T) / (237.7 + T) + ln(RH / 100)
T_d = (237.7 × γ) / (17.27 - γ)

For cooling and humidity management in building HVAC systems, reference our AC Tonnage Calculator.

Human Comfort and Indoor Humidity Scale

Dew point provides a more accurate indicator of human comfort than relative humidity alone:

  • Below 50°F (10°C): Very dry, crisp air.
  • 50°F to 55°F (10°C to 13°C): Optimal comfort for most people.
  • 56°F to 60°F (13°C to 16°C): Noticeable humidity, generally comfortable.
  • 61°F to 65°F (16°C to 18°C): Sticky and humid.
  • Above 65°F (18°C+): Oppressive, muggy, high condensation risk.
Project worksheet

What are your dew point inputs?

Liquid-water dew-point approximation within a stated input range, distinct from wet-bulb temperature.

Measurement units

How do I embed this calculator?

Frequently asked questions

What questions come up about this calculation?

What is the formula to calculate dew point?

Dew point is computed using the Magnus formula: T_d = (237.7 × γ) / (17.27 - γ), where γ = (17.27 × T) / (237.7 + T) + ln(RH/100).

What dew point is considered comfortable?

A dew point between 50°F and 55°F is considered universally comfortable. Once the dew point exceeds 65°F, the air feels muggy and oppressive.

Sources

Which sources support this calculation?

  1. NIST: SI units and measurement
  2. National Weather Service: humidity and dewpoint equations
Created by

Who created this dew point calculator?

Jamie C.

Across her work, Jamie focuses on bridging operational precision with practical technology adoption. She develops industry-specific calculators, software guides, and technical content tailored to the construction, residential living, HVAC, and artificial intelligence sectors. By pairing hands-on systems design with advanced AI and automation workflows, her resources empower trade specialists, contractors, and growing teams to eliminate bottlenecks, forecast project requirements accurately, and run more efficient operations. Fluent in five languages, Jamie approaches every tool and article with an emphasis on clarity, actionable utility, and real-world results.

View author articles ↗
From the blog

Which related articles can help you plan?

How do I cite this tool?

Copy the citation below.