Dew Point Calculator
Adjust the inputs below. Results update as you type.
How it works
Dew point is the temperature at which air becomes saturated and condensation begins. Magnus formula: Td = (243.04 × γ) / (17.625 − γ), where γ = ln(RH/100) + 17.625T/(243.04+T). A dew point above 60°F feels humid; above 70°F is oppressive. Dew point is more reliable than relative humidity for gauging human comfort because it doesn't change with air temperature.
Input guidance
- Confirm date/time/unit settings before comparing outputs.
- If a task has optional fields, run both with and without them to understand impact.
- Save scenario variants when making practical decisions.
The formula
Dew point is the temperature at which air becomes saturated. The Magnus approximation derives it from temperature and relative humidity.
Worked example
At 25°C and 60% humidity, the dew point is about 16.7°C — cooling the air to that point would form dew or fog.
More examples to test
- Quick-pass example: run default assumptions for a first estimate.
- Refined example: update one assumption at a time to isolate impact.
How to interpret results
Use outputs as operational estimates and pair them with local constraints, business rules, or provider requirements.
When this can be inaccurate
Utilities can miss local policy details, special-case rules, and environment-specific constraints.
Change history
- July 2026: Quality-reviewed for publication with formula checks and explanatory copy updates.
Site-wide corrections also appear on the corrections log.
Find productivity tools for everyday workflows
General recommendation, not professional advice.
Frequently asked questions
What is the dew point?+
The temperature to which air must cool for water vapor to condense. A higher dew point means more moisture and muggier air.
How is dew point different from humidity?+
Relative humidity is a percentage that changes with temperature; dew point is an absolute measure of moisture that feels more intuitive for comfort.
What dew point feels humid?+
Above about 16°C (60°F) air feels sticky; above 21°C (70°F) it feels oppressive. Lower dew points feel comfortable or dry.
Why are outputs slightly different from another tool?+
Different tools can use different rounding rules, default assumptions, and treatment of edge cases.
How can I improve estimate reliability?+
Use verified inputs from real records and re-run calculations after major assumption changes.