Relative humidity to absolute humidity formula

[SG4891]

Hello, I have a home automation device that knows atmospheric pressure (hPa), outside temperature(C)/humidity(%) and inside temp/humidity. I am looking for a formula that uses those inputs to Absolute humidity in kg/m3, but I'm struggling because I'm a programmer, I don't have a background in science and mathematics, I get lost combining formulas. My goal is to estimate the relative humidity of fresh air pulled in from outside and heated to inside temperature (to avoid increasing the relative humidity inside when pulling cold air). I hope that was clear, thank you for your help, I'm sure is easier than it looks, but I have been looking for a while without finding a clear answer.

[MegaMike]

On 3/30/2021 at 10:03 PM, SG4891 said:

Hello, I have a home automation device that knows atmospheric pressure (hPa), outside temperature(C)/humidity(%) and inside temp/humidity. I am looking for a formula that uses those inputs to Absolute humidity in kg/m3, but I'm struggling because I'm a programmer, I don't have a background in science and mathematics, I get lost combining formulas. My goal is to estimate the relative humidity of fresh air pulled in from outside and heated to inside temperature (to avoid increasing the relative humidity inside when pulling cold air). I hope that was clear, thank you for your help, I'm sure is easier than it looks, but I have been looking for a while without finding a clear answer.

This methodology looks reasonable: https://carnotcycle.wordpress.com/2012/08/04/how-to-convert-relative-humidity-to-absolute-humidity/

You won't even need to convert your temperature (C) or relative humidity (%)... Just plug n' chug. To get kg/m3 from g/m3, just multiple g/m3 by 1kg/1000g == 1/1000.