Compute vapor pressure, humidity, dew point, and density precisely. Review formulas, examples, exports, charts, and practical interpretation for better analysis.
| Case | Temperature (°C) | Pressure (kPa) | RH (%) | Sat. Vapor Pressure (kPa) | Actual Vapor Pressure (kPa) | Dew Point (°C) | Absolute Humidity (g/m³) |
|---|---|---|---|---|---|---|---|
| Lab Air | 20 | 101.325 | 50 | 2.338 | 1.169 | 9.26 | 8.64 |
| Humid Room | 28 | 100.800 | 75 | 3.779 | 2.834 | 23.18 | 20.40 |
| Dry Chamber | 35 | 99.500 | 30 | 5.622 | 1.687 | 14.82 | 11.72 |
Water vapor calculations connect temperature, pressure, and moisture content. The calculator uses standard psychrometric relationships for saturation pressure, actual vapor pressure, dew point, and humidity metrics.
es = 0.6108 × exp[(17.27 × T) / (T + 237.3)]
Here, T is air temperature in degrees Celsius, and es is saturation vapor pressure in kilopascals.
ea = (RH / 100) × es
This gives the actual partial pressure of water vapor present in air.
γ = [17.27 × T / (237.3 + T)] + ln(RH / 100)
Td = [237.3 × γ] / [17.27 - γ]
AH = (2.16679 × ea(Pa)) / T(K)
This produces water vapor mass concentration in grams per cubic meter.
w = 0.622 × ea / (P - ea)
Here, P is total air pressure, and w is kilograms of vapor per kilogram of dry air.
q = w / (1 + w)
VPD = es - ea
VPD shows how strongly air can still absorb moisture.
Water vapor is the gaseous phase of water present in air. It changes with temperature, pressure, and nearby liquid water sources. In physics, it strongly affects phase equilibrium, thermal transport, atmospheric stability, and mass transfer behavior.
Vapor pressure measures the partial pressure exerted by water molecules in air. Saturation vapor pressure rises rapidly with temperature. That rise explains why warm air can hold much more moisture than cold air under the same total pressure.
Relative humidity compares actual vapor pressure to the saturation limit. It does not show total water mass directly. Instead, it tells how close air is to condensation. Two air samples can share the same relative humidity while containing different moisture amounts.
Dew point is the temperature at which air becomes saturated during cooling at constant pressure and moisture content. When a surface temperature falls below dew point, condensation begins. This concept is important for HVAC design, storage, optics, and weather analysis.
Absolute humidity expresses the mass of water vapor per unit volume. It is useful when engineers study drying, ventilation, chamber control, and gas mixtures. Water vapor density also influences buoyancy, sensor calibration, and combustion air evaluation.
Mixing ratio compares vapor mass with dry air mass. Specific humidity compares vapor mass with total moist air mass. These measures stay useful in atmospheric science because they are less sensitive to temperature changes than relative humidity.
Vapor pressure deficit describes the gap between saturation and actual vapor pressure. A higher deficit means stronger evaporation potential. It is widely used in plant science, drying systems, climate control, and laboratory moisture management.
This calculator combines several related moisture properties in one interface. It helps students, researchers, and engineers move from basic inputs to interpretable outputs quickly. The result panel, chart, exports, and example table support both learning and practical reporting.
It computes saturation vapor pressure, actual vapor pressure, dew point, relative humidity, absolute humidity, mixing ratio, specific humidity, vapor pressure deficit, and water vapor density from the entered air condition.
Atmospheric pressure affects moist air relationships, especially mixing ratio and specific humidity. Using local pressure improves realism, particularly for elevated locations, pressurized systems, and controlled environmental chambers.
It is the maximum vapor pressure possible at a given temperature when air is in equilibrium with liquid water. Beyond this limit, condensation begins if extra moisture is added.
Dew point is a temperature value tied to condensation onset. Relative humidity is a percentage showing how close the air is to saturation at its current temperature.
As temperature rises, saturation vapor pressure rises strongly. That means the equilibrium limit for water vapor becomes higher, allowing more moisture to remain in gaseous form.
It shows the remaining moisture-holding capacity of air. Larger values indicate stronger evaporation or transpiration potential, which matters in drying, agriculture, and climate control.
Yes. The calculator lets you choose either relative humidity or dew point as the moisture input. It then derives the missing moisture properties from that selected mode.
It is useful in physics education, HVAC studies, atmospheric analysis, greenhouse control, laboratory environments, drying systems, storage planning, and condensation risk assessment.
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.