How this is calculated
Inspect the versioned inputs.
| Constant | Value | Scope & source |
|---|---|---|
| fahrenheitScale | 1.8 Fahrenheit interval per Celsius interval | Exact conversion ratio. nist-temperature-conversion ↗ Verified 2026-11-08 |
| fahrenheitOffset | 32 degrees Fahrenheit | Exact conversion offset. nist-temperature-conversion ↗ Verified 2026-11-08 |
| antoineA | 4.6543 NIST log10(bar), kelvin convention coefficient | One continuous fit for the humidity model. Valid upper temperature is 99.85°C; at 100°C or above show out-of-range rather than silently extrapolating. nist-water-antoine ↗ Verified 2026-11-08 |
| antoineB | 1435.264 K | One continuous fit for the humidity model. Valid upper temperature is 99.85°C; at 100°C or above show out-of-range rather than silently extrapolating. nist-water-antoine ↗ Verified 2026-11-08 |
| antoineC | -64.848 K | One continuous fit for the humidity model. Valid upper temperature is 99.85°C; at 100°C or above show out-of-range rather than silently extrapolating. nist-water-antoine ↗ Verified 2026-11-08 |
| antoineMinK | 255.9 K | One continuous fit for the humidity model. Valid upper temperature is 99.85°C; at 100°C or above show out-of-range rather than silently extrapolating. nist-water-antoine ↗ Verified 2026-11-08 |
| antoineMaxK | 373 K | One continuous fit for the humidity model. Valid upper temperature is 99.85°C; at 100°C or above show out-of-range rather than silently extrapolating. nist-water-antoine ↗ Verified 2026-11-08 |
| waterMolarMass | 0.0180153 kilograms per mole | NIST's molecular weight converted from grams per mole. nist-water-antoine ↗ Verified 2026-11-08 |
| gasR | 8.31446261815324 joules per mole per kelvin | SI molar gas constant. nist-gas-constant ↗ Verified 2026-11-08 |
Input defaults that are not sourced measurements are illustrative planning assumptions. Exact unit definitions, the 52-week convention and algorithm details are in the shared methodology.
Worked example
An example you can inspect.
80°C converts to 176°F. In the simplified model, increasing water or the assumed evaporated fraction raises theoretical RH; actual löyly is localized and changes over time.
Keep the conversion and vapor model separate.
The temperature converter uses the exact relationship between Celsius and Fahrenheit. The water-vapor estimate uses a temperature-bounded Antoine fit and an ideal-gas calculation. A temperature can therefore convert successfully while being outside the validated range used by this particular vapor-pressure fit. The tool reports that limit instead of extending the coefficients beyond their documented domain. A valid conversion alone does not make the separate humidity model valid at that temperature.
Interpret a ladle scenario as a simplified thought experiment.
The entered evaporation fraction specifies how much added water the model assumes becomes vapor. The calculation holds air temperature and room volume fixed and treats the room as sealed and uniform. A real room exchanges air and has changing temperatures, surfaces and local vapor concentrations. The displayed humidity change therefore illustrates the accounting assumptions; it is not a prediction of the peak at a person's face. A saturation flag means the raw estimate exceeded the model's available vapor capacity, not that a larger ladle has been shown acceptable.
Questions, considered
Questions about this tool
How should I interpret the temperature & humidity converter result?
The humidity fit stops at 99.85°C. The model assumes a sealed, uniformly mixed room at fixed temperature, and ignores heat exchange, ventilation, absorption and condensation dynamics. It does not predict perceived heat or a safe ladle size. Convert temperature exactly and explore a bounded, fixed-temperature water-vapor model that makes its evaporation and mixing assumptions visible.
Which assumptions matter in the temperature & humidity converter?
°F = 1.8 × °C + 32. Temperature conversion is separate from the humidity model. NIST Antoine fit gives log₁₀(Pbar) = A − B/(TK + C), valid only from 255.9 to 373 K. Added vapor pressure follows nRT/V. Add the entered evaporated water mass at fixed temperature; report capped RH and flag a theoretical result above saturation. No feels-like temperature is invented.
Primary sources
Follow the source.
- NIST Guide to the SI, Appendix B.9: Factors for units listed by kind of quantity or field of science ↗
Temperature entries
Celsius=(Fahrenheit−32)/1.8; Kelvin=Celsius+273.15. Conversion does not establish a safe personal sauna temperature.
Checked 2026-11-08 - NIST Chemistry WebBook, SRD 69 — Water ↗
Molecular weight; Phase change data; Antoine Equation Parameters, SI/bar table
The SI table uses Kelvin and bar: log10(P)=A−B/(T+C). Stull's coefficients cover 255.9–373 K continuously. Bridgeman/Aldrich provides narrower overlapping fits. Do not mix the calorie/atm table's A coefficient with SI/bar. Never extrapolate a chosen fit outside its documented interval.
Checked 2026-11-08 - NIST FEASST physical_constants documentation — MolarGasConstant ↗
MolarGasConstant().value()
Returns 8.31446261815324 in SI. The 2022 CODATA table also lists the molar gas constant as exact.
Checked 2026-11-08 - Equation Of State (Ideal Gas) — NASA Glenn Research Center ↗
pV=nRT
Use the ideal-gas relation for a simplified well-mixed water-vapor mass balance. Real heat/mass transfer, ventilation, evaporation and condensation require more than this model.
Checked 2026-11-08