Air Props app allows you to enter the altitude you are at, the temperature, and relative humidity, and it will calculate for you the air density for dry conditions (0% relative humidity), for the relative humidity conditions you entered, and the pressure of air at that elevation you entered.
You can enter data and have it report in either English or metric units.
It will also generate a message for you checking to see if the data entered is within normal ranges (e.g., enter 101% relative humidity, it will flag you with wrong data entry).
See screen shots below for more of what this app delivers for you.
For estimates and informational purposes only.