Estimate dew point, relative humidity or air temperature with a documented Magnus approximation, clear units and temperature-spread visualization.
01 / AIR & MOISTURE
A documented Magnus approximation over liquid water. It is an estimate, not a humidity-sensor or laboratory measurement.
02 / HUMIDITY RELATIONSHIP
Cooling a surface toward the estimated dew point can allow water vapor to condense, depending on conditions. Below freezing it may form frost. These numbers do not determine a universal comfort, health or equipment threshold.
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Choose the quantity to find, enter the two known atmospheric quantities and select Celsius or Fahrenheit. Review the model range and any withheld solution instead of treating an approximation as a measurement.
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The liquid-water approximation uses a = 17.625 and b = 243.04°C. For air temperature T and RH in percent, γ = ln(RH/100) + aT/(b+T), then dew point Td = bγ/(a−γ). Both modeled temperatures are restricted to −40…50°C.
Yes. Relative humidity is 100 times exp(g(Td) minus g(T)), where g(x) = ax/(b+x). Air temperature uses g(Td) minus ln(RH/100) in the inverse expression. The same coefficients and supported range apply in every mode.
At 0% RH the logarithm has no finite dew-point solution, so a numeric dew point is withheld. Air temperature cannot be recovered from a finite dew point and zero RH either. At 100% RH, dew point equals air temperature within the supported model.
It implies relative humidity above 100%, or supersaturation. This calculator does not support that condition and does not silently clamp it to a normal-humidity result. Inputs and extrapolated inverse solutions must remain in the stated approximation range.
No. Dew point relates to saturation as air/surfaces cool. Heat index and wet-bulb temperature describe different processes and are not computed here. Below freezing, a liquid-water dew-point approximation also differs from an ice-based frost point.
The spread is air temperature minus dew point, using proper temperature-difference conversion between Celsius and Fahrenheit. The markers show actual model values on a fixed supported scale; the RH bar is a saturation ratio, not water’s volume share in air. No universal comfort, health or equipment guarantee is inferred.