Absolute Humidity Calculator 2026
Calculate absolute humidity, water vapour density, and dew point instantly from temperature and relative humidity using the Magnus-Tetens formula.
Air Conditions
Enter temperature and relative humidity to calculate absolute humidity
Typical UK room temperature is 18-22°C. Outdoor temperatures vary widely by season.
The relative humidity reading from your hygrometer or weather station (0-100%).
Adjusts atmospheric pressure for high-altitude locations. Leave as 0 for sea level.
Humidity Results
Absolute humidity, vapour pressure, and dew point
Enter temperature and relative humidity above and click Calculate Absolute Humidity to see your full psychrometric profile.
Absolute Humidity at Common Conditions
Typical absolute humidity values (g/m³) at different temperatures and relative humidity levels, based on the Magnus-Tetens saturation vapour pressure formula.
| Temperature | RH 30% | RH 50% | RH 70% | RH 90% |
|---|---|---|---|---|
| 0°C | 1.45 g/m³ | 2.42 g/m³ | 3.39 g/m³ | 4.36 g/m³ |
| 10°C | 2.81 g/m³ | 4.69 g/m³ | 6.57 g/m³ | 8.45 g/m³ |
| 20°C | 5.20 g/m³ | 8.66 g/m³ | 12.13 g/m³ | 15.59 g/m³ |
| 25°C | 6.92 g/m³ | 11.53 g/m³ | 16.15 g/m³ | 20.76 g/m³ |
| 30°C | 9.08 g/m³ | 15.13 g/m³ | 21.18 g/m³ | 27.23 g/m³ |
| 35°C | 11.78 g/m³ | 19.63 g/m³ | 27.49 g/m³ | 35.34 g/m³ |
Absolute Humidity FAQ
Everything you need to know about absolute humidity, dew point, and how they differ from relative humidity.
Absolute humidity is the total mass of water vapour present in a given volume of air, usually expressed in grams per cubic metre (g/m³). Unlike relative humidity, which is a percentage relative to the maximum amount of moisture air can hold at a given temperature, absolute humidity is a direct measurement of water content that does not change with temperature unless moisture is added or removed.
Absolute humidity is calculated using the formula AH = (RH/100) × Es × 2.1674 / (273.15 + T), where Es is the saturation vapour pressure (calculated via the Magnus-Tetens formula), RH is relative humidity as a percentage, and T is temperature in degrees Celsius. The saturation vapour pressure formula is Es = 6.112 × exp((17.62 × T) / (243.12 + T)), measured in hectopascals (hPa).
Relative humidity is a percentage that compares the current amount of water vapour in the air to the maximum amount the air could hold at that specific temperature. Absolute humidity is a fixed measurement (grams of water per cubic metre of air) that represents the actual mass of water vapour present, regardless of temperature. As temperature rises, air can hold more moisture, so relative humidity can drop even if absolute humidity stays the same.
Dew point is the temperature at which air becomes fully saturated with water vapour (100% relative humidity) and condensation begins to form. It is directly related to absolute humidity — the higher the absolute humidity, the higher the dew point. Dew point is considered a more reliable indicator of how humid the air actually feels, since it does not change with temperature the way relative humidity does.
A comfortable indoor absolute humidity level typically falls between 7 and 12 grams per cubic metre (g/m³), corresponding to a relative humidity of 40-60% at typical room temperatures of 20-22°C. Levels below 7 g/m³ can feel dry and cause skin irritation, while levels above 12 g/m³ can feel sticky, promote mould growth, and create an uncomfortable environment.
Absolute humidity is critical for HVAC system design, dehumidifier sizing, industrial drying processes, and greenhouse climate control because it represents the actual mass of water vapour that needs to be added or removed from the air. Unlike relative humidity, it allows engineers to perform precise mass-balance calculations for moisture removal rates, condensation risk assessment, and psychrometric chart analysis.