EN
SV
Convert to absolute humidity
101,325 kPa at sea level, 89,87 kPa at 1000 m above sea levelAbsolute Humidity Calculator (Celcius)
Absolute Humidity Calculator (Fahrenheit)
Convert to relative humidity
101,325 kPa at sea level, 89,87 kPa at 1000 m above sea levelRelative Humidity Calculator (Celcius)
Relative Humidity Calculator (Fahrenheit)
Unlocking Air Moisture: The Absolute Humidity Calculator
Discover the practicality of our tool doing the conversion of relative humidity to absolute humidity and vice versa. Experience the convenience of obtaining precise conversions effortlessly.
Information on the parameters needed to describe the amount of water in air;
Atmospheric Pressure (kPa)
The pressure changes with the weather with lower pressure at bad weather and high pressure when the sun is shining. At low pressure the air gets lighter and rises which creates clouds and wind. At high pressure the air has a higher density which creates a down motion and a higher stability.
For us within the desiccant dehumidification business the standard is to calculate with nominal pressure which is 101,325 kPa at sea level. You do not normally calculate with bad or good weather.
What we do need to consider is the altitude of the installation place. If you are for example in parts of Nevada in USA, around Nairobi in Kenya or around Amman in Jordan you have altitudes above 1000 m which affects the flow-charts rather much. With fresh air in the dehumidification system we in most cases have pre-coolers to take down the moisture content before drying the air in the desiccant rotor. If you for example pre-cool moist outdoor air to 10°C (50°F) at sea level you get an absolute water content at 7,6 g/kg (53,2 gr/lb). If you are in Nairobi at 1700 m you have a nominal pressure at 82,5 kPa and then you come down to 9,4 g/kg (65,8 gr/lb) with a pre-cooler of 10°C before the desiccant rotor. You can check this by changing the pressure on the top of the calculator, write in 10°C or 50°F and 100%RH and then click Calculate.
Table of atmospheric pressure at different altitudes;
- 200m
- 400m
- 600m
- 800m
- 1000m
- 1200m
- 1400m
- 1600m
- 1800m
- 2000m
- 98,95 kPa
- 96,61 kPa
- 94,32 kPa
- 92,08 kPa
- 89,87 kPa
- 87,72 kPa
- 85,60 kPa
- 83,52 kPa
- 81,49 kPa
- 79,50 kPa
Temperature (°C or °F)
The most well-known parameter of our air as it is the main parameter for our own comfort.
With higher temperature the air can contain more humidity in vapour form. Check this out by increasing the temperature in the Calculator but keep the same relative humidity and see that the moisture content (g/kg or gr/lb) increases. The physics behind this is that with higher temperature the water molecules in the air moves faster and is less willing to go into liquid phase.
Relative Humidity (%RH)
A parameter most people recognise as we indirectly can feel it. At low relative humidity the sweat on your skin easily evaporates and sweating is an effective way to keep our bodies in temperature thanks to the evaporative cooling. At higher relative humidity the cooling is less effective.
The physics is that at 100%RH the water in the air goes from vapour to liquid form, condensate on a cold surface or become mist in the air. The number describes the water partial pressure in the air compared to the pressure it will be saturated. This is almost linear to the water content also so 50%RH will be half the absolute humidity compared to the 100%RH number at the same temperature.
Absolute humidity (g/kg or gr/lb)
Describes the weight of water vapour in the air. The number is weight of water compared to weight of dry air.
This number is very useful in an air handling process as it stays the same if you change the temperature unless you hit the condensation line and take out water from the air. Also in the condensation part of an air handler it is good to use as it is easy to calculate the amount of water you condensate.
Dew-point (°Cdp or °Fdp)
The temperature you need to cool down the air to in order to go from water vapour to liquid form. Like absolute humidity this number does not change with temperature unless you come down to the dew-point temperature. If the air temperature and dew-point is the same you have 100%RH.
This is useful in many ways. For projects with very dry air, Lithium battery manufacturing for example, it is easier to talk about dew-point instead of absolute humidity as the decimals gets so many on the g/kg or gr/lb. To avoid condensation in a process this parameter is also very useful, just keep the dew-point of the air lower than the surface temperature and that surface will remain dry.
