Analyze moisture content using trusted atmospheric relationships quickly. Switch inputs, convert units, and view pressures. Save tables and results for engineering notes and audits.
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| Method | Inputs | Relative Humidity | Vapor Pressure (hPa) |
|---|---|---|---|
| Temperature + Dew Point | T = 25°C, Td = 18°C | ≈ 64% | ≈ 20.6 |
| Pressures | e = 16.5 hPa, es = 31.7 hPa | ≈ 52% | 16.5 |
| Dry + Wet Bulb | Tdb = 30°C, Twb = 24°C, P = 1013 hPa | ≈ 58% | ≈ 24.6 |
Examples are rounded and may vary with assumptions.
These equations provide practical engineering accuracy for typical ambient conditions.
Relative humidity (RH) compares the air’s water vapor content to the maximum it can hold at the same temperature. Because warm air can hold more vapor, RH can drop quickly during heating, even if the moisture amount stays constant. RH influences comfort, evaporation rate, corrosion risk, and electrostatic discharge.
Saturation vapor pressure rises nonlinearly with temperature. Around typical indoor conditions, a few degrees of warming can increase saturation pressure noticeably, lowering RH unless vapor pressure also increases. This calculator converts units and applies standard vapor pressure relationships to keep results consistent across common measurement systems.
Dew point is the temperature at which air becomes saturated at constant pressure. It tracks actual moisture more directly than RH. When dew point is close to air temperature, RH is high and condensation is more likely on cool surfaces. The calculator estimates vapor pressure from dew point and then computes RH.
If you already know actual vapor pressure e and saturation vapor pressure es, RH is a straightforward ratio: RH = 100 × (e/es). This approach is helpful in lab settings, HVAC analysis, and atmospheric datasets where vapor pressures are reported or derived from mixing ratios.
Wet-bulb temperature reflects evaporative cooling and provides a practical way to estimate humidity when sensors measure dry bulb, wet bulb, and pressure. The calculator uses a common psychrometric approximation to estimate vapor pressure from these values. Results are suitable for engineering checks and routine monitoring.
Along with RH, the tool reports vapor pressure, saturation vapor pressure, dew point checks, and absolute humidity (g/m³). Absolute humidity helps compare moisture levels across different temperatures, while vapor pressure supports process calculations such as drying, ventilation sizing, and moisture balance studies.
For many workplaces, 40–60% RH is often targeted to balance comfort and material protection. Below 30% RH, dryness and static issues become more common. Above 70% RH, mold risk increases on cool surfaces and in poorly ventilated zones. Use measurements from reliable sensors and stable sampling locations.
Humidity calculations depend on temperature accuracy, sensor calibration, and pressure assumptions. For best results, record temperatures to at least 0.1°C and pressure when using wet-bulb inputs. Avoid measuring near vents or wet surfaces. Export CSV or PDF to document conditions, methods, and derived values clearly.
It is how “full” the air is with water vapor compared with the maximum possible at the same temperature. It is a percentage, not a direct measure of moisture amount.
Warming increases the saturation vapor pressure. If the actual moisture stays the same, the ratio e/es decreases, so RH falls even without dehumidifying.
Use temperature + dew point when you have a dew point reading. Use pressures when vapor pressures are known. Use dry bulb + wet bulb + pressure for sling-psychrometer style measurements.
Yes, in normal unsaturated air. At saturation, dew point equals air temperature. If dew point appears higher, it usually indicates a measurement or unit entry issue.
Absolute humidity (g/m³) estimates the mass of water vapor per cubic meter of air. It helps compare moisture content across different temperatures where RH can be misleading.
Pressure affects the psychrometric relationship between wet-bulb depression and vapor pressure. Using local pressure improves the vapor pressure estimate and the resulting RH.
For typical ambient conditions, the equations provide practical accuracy. For high-precision work, use calibrated instruments and validated psychrometric charts or standards, then compare with the calculator’s outputs.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.