Science & Engineering
Dew Point Calculator
Estimate dew point from air temperature and relative humidity using the Magnus approximation. The calculator uses dew point = b × γ(T,RH) ÷ (a − γ(T,RH)). It returns more than one result so you can check the main answer against a useful secondary measure. Dew point tracks absolute moisture more directly than relative humidity and approaches air temperature at saturation. This approximation is suitable for ordinary weather conditions, not precision psychrometric or industrial design.
Educational model only. Use applicable standards, calibrated measurements, and qualified review for safety-critical work.
Calculate and compare
Use the number box for precision or the slider for fast scenario testing.
Scenario results
Dew point
16.7 °C
Magnus approximation.
Temperature-dew point spread
8.3 °C
Smaller spread means air is closer to saturation.
Dew point in Fahrenheit
62.06 °F
Converted result.
How the calculation works
Use consistent units and retain full precision until the final display step.
Worked example
Reproduce the displayed scenario, then change one assumption at a time.
Assumptions behind the result
- • Inputs use the units shown beside each control.
- • The displayed formula is applied without hidden market or demographic data.
- • Rounding occurs only for display; calculations keep full numeric precision.
- • Dew point tracks absolute moisture more directly than relative humidity and approaches air temperature at saturation.
- • This approximation is suitable for ordinary weather conditions, not precision psychrometric or industrial design.
Mistakes that change the answer
- • Mixing percentages with decimals or mixing incompatible units.
- • Relying on a rounded intermediate value instead of the full result.
- • Changing several assumptions at once instead of testing air temperature separately.