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Dew Point Calculator

Use this dew point calculator to review an educational health calculation for dew point.

Primary answer
Dew point
Inputs to verify
Air temperature, Temperature unit, and Relative humidity
Use type
Use as an estimate that depends on assumptions.
Keyword intent
dew point calculator

Calculator

Dew Point Calculator

Calculates dew point from air temperature, temperature unit, relative humidity. Defaults are filled in so you can review a working example before changing inputs.

selected

Enter air temperature; it must convert to -80 C through 60 C.

Choose Fahrenheit or Celsius.

%

Enter relative humidity as a percent greater than 0 and no more than 100.

Result

Result reflects the current submitted inputs.

  • Risk B
  • Reviewed 2026-05-26
  • 3 sources
Dew point55.1 F
Dew point12.8 C
Air temperature used23.9 C
Relative humidity used50%
Formula methodAugust-Roche-Magnus approximation
Saturation statusAir is not saturated

Breakdown

Air temperature used
23.8889 C
Relative humidity used
50%
Magnus a constant
17.625
Magnus b constant
243.04 C
  • The formula uses Celsius internally with August-Roche-Magnus constants 17.625 and 243.04 C.
  • Relative humidity must be greater than 0% and no more than 100%.
  • The supported temperature range is -80 C through 60 C.
  • This is an empirical weather/HVAC estimate, not a frost-point, wet-bulb, mold-risk, medical, or professional psychrometric determination.
  • Intermediate values are not rounded; raw outputs are rounded for stable tests and display formatting is separate.

Accuracy notes

Risk level
B
Reviewed
2026-05-26
Sources
3
Primary result
Dew point

Formula logic is kept in a pure calculator module with fixtures, source notes, and page-visible assumptions.

Categories

What the result means

Use Dew point as the headline answer for dew point. Estimated dew point in Fahrenheit. Treat the result as educational context, then read the limitations and assumptions before discussing it with a professional. Use air temperature used, relative humidity used, and formula method to explain why dew point moved when an input changed. Record the inputs you used and verify any health concern with a qualified professional.

Dew pointEstimated dew point in Fahrenheit.
Dew pointEstimated dew point in Celsius.
Air temperature usedAir temperature normalized to Celsius before calculation.
Relative humidity usedRelative humidity used by the formula.

Use the result this way

  1. Start with Dew point, then use supporting outputs only to explain the primary answer.
  2. Verify air temperature, temperature unit, and relative humidity before copying the result.
  3. Choose the mode or method first because it can change which formula is applied, keep units consistent with the labels shown in the form, and stay within the documented minimum and maximum ranges.
  4. Record the inputs you used and verify any health concern with a qualified professional.

User job

How to use this calculator

Use Dew Point Calculator when you need dew point, then use dew point and air temperature used to check the context for general wellness education and preparing for a professional conversation.

Best for

  • Understanding a formula-based estimate
  • Seeing which inputs drive a health-related output
  • Reviewing a default example before entering your own air temperature and temperature unit.

Check before relying

  • Health formulas can be population-specific; do not use the result as diagnosis or treatment advice.
  • The formula uses Celsius internally with August-Roche-Magnus constants 17.625 and 243.04 C.
  • Relative humidity must be greater than 0% and no more than 100%.
  • Source context: United States Environmental Protection Agency, reviewed 2026-05-26.

Next useful step

  • Heat Index CalculatorUse next when you need heat index from air temperature and temperature unit after checking dew point.
  • Wind Chill CalculatorUse next when you need wind chill from air temperature and temperature unit after checking dew point.
  • One Rep Max CalculatorUse next when you need estimated 1RM from weight lifted and weight unit after checking dew point.

Formula

The calculator inverts the August-Roche-Magnus RH relation: gamma = ln(RH/100) + 17.625T/(243.04+T), then Td = 243.04gamma/(17.625-gamma). Key assumptions: The formula uses Celsius internally with August-Roche-Magnus constants 17.625 and 243.04 C. Relative humidity must be greater than 0% and no more than 100%. The supported temperature range is -80 C through 60 C.

  • The calculator inverts the August-Roche-Magnus RH relation: gamma = ln(RH/100) + 17.625T/(243.04+T), then Td = 243.04gamma/(17.625-gamma).
  • The formula uses Celsius internally with August-Roche-Magnus constants 17.625 and 243.04 C.
  • Relative humidity must be greater than 0% and no more than 100%.
  • Primary source context: United States Environmental Protection Agency.

Inputs

Enter air temperature, temperature unit, and relative humidity for general wellness education and preparation for a professional conversation. Before calculating, choose the mode or method first because it can change which formula is applied, keep units consistent with the labels shown in the form, and stay within the documented minimum and maximum ranges. Air temperature: Enter air temperature; it must convert to -80 C through 60 C. Temperature unit: Choose Fahrenheit or Celsius. Relative humidity: Enter relative humidity as a percent greater than 0 and no more than 100.

Air temperatureEnter air temperature; it must convert to -80 C through 60 C.
Temperature unitChoose Fahrenheit or Celsius.
Relative humidityEnter relative humidity as a percent greater than 0 and no more than 100.

Example

Using the default inputs, Dew Point Calculator returns dew point of 55.1 F. Adjust air temperature, temperature unit, and relative humidity to match your own scenario.

FAQ

How is dew point calculated here?

The calculator inverts the August-Roche-Magnus RH relation: gamma = ln(RH/100) + 17.625T/(243.04+T), then Td = 243.04gamma/(17.625-gamma). The first assumption to check is: The formula uses Celsius internally with August-Roche-Magnus constants 17.625 and 243.04 C.

What does Dew point mean for dew point?

Treat the result as educational context, then read the limitations and assumptions before discussing it with a professional. Secondary values such as air temperature used, relative humidity used, and formula method are there to explain the primary answer, not to replace it.

What should I enter for Air temperature?

Enter air temperature; it must convert to -80 C through 60 C. Use selected for this field. Choose the mode or method first because it can change which formula is applied, keep units consistent with the labels shown in the form, and stay within the documented minimum and maximum ranges.

How does Temperature unit change dew point?

Choose Fahrenheit or Celsius. Changing it can alter dew point because the formula uses the submitted inputs together. Also compare measurement method, formula population, age range, units, sex or activity assumptions, and clinical context.

Why does the dew point example show 55.1 F for dew point?

The default inputs produce 55.1 F for dew point. Treat that as a format and scale check, then replace every default value with your own inputs.

Can the dew point result diagnose or prescribe anything?

No. Use it as educational context only. Health formulas can depend on population, measurement method, age range, and clinical context.

Sources

Last reviewed: 2026-05-26

  • Reviewed 2026-05-26
    HMS Meteorology Humidity AlgorithmsUnited States Environmental Protection Agency. Constants 17.625 and 243.04 C and the RH relationship inverted by this calculator to solve dew point.
    Scope
    EPA humidity algorithm page using the August-Roche-Magnus relationship for relative humidity from air temperature and dew point.
    Supports
    Constants 17.625 and 243.04 C and the RH relationship inverted by this calculator to solve dew point.
  • Reviewed 2026-05-26
    Dew Point and Relative Humidity CalculationsNOAA / National Weather Service Weather Prediction Center. Weather-domain scope and relationship between temperature, dew point, and relative humidity.
    Scope
    NOAA/WPC public calculator context for dew point and relative humidity calculations.
    Supports
    Weather-domain scope and relationship between temperature, dew point, and relative humidity.
  • Reviewed 2026-05-26
    READY Tools - Moisture CalculatorNOAA Air Resources Laboratory. Independent NOAA calculator context for atmospheric moisture quantities and future expansion boundaries.
    Scope
    NOAA atmospheric moisture calculator accepting air temperature, dew point, wet bulb, and relative humidity inputs.
    Supports
    Independent NOAA calculator context for atmospheric moisture quantities and future expansion boundaries.

Disclaimer

This health calculator is for educational estimates only. It does not diagnose, treat, or replace advice from a qualified health professional.