Calculating Density Alttitude of Air knoing temp/baro/humidity?

[soundengineer]

I'm trying to figure out the Density Altitude of Air
Known data
Temp 70*F
Barometric Pressure 30inHg
Humidity 35%

do I need more data or can I calculet it from this?

 

[nucleus]

There are many calculators available to do this. One is at:
http://www.srh.noaa.gov/epz/wxcalc/wxcalc.shtml
With this one you need to calculate Dewpoint temp first using the first moisture calculator then calculate the density altitude.
BTW humidity when it is in a % is relative humidity.

 

[soundengineer]

There are many calculators available to do this. One is at:
http://www.srh.noaa.gov/epz/wxcalc/wxcalc.shtml
With this one you need to calculate Dewpoint temp first using the first moisture calculator then calculate the density altitude.
BTW humidity when it is in a % is relative humidity.

I need an actual formula...not a calculator
calculator doesn't do me any good in an excel spreadsheet...

so what's the formula for dewpoint with known temperature and relative humidity
and then once I have dewpoint how do I get to Density Altitude?

 

[nucleus]

The formulas are on the site I gave you. There are also spreadsheets on the net that do what you want to do.
As for Td some reports already include it.