Air Density Calculator
Air density from temperature, pressure and altitude.
Enter your values
Enter the air temperature in °C.
Enter the altitude in m.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Air density
- 1.2041 kg/m³
- In lb/ft³
- 0.07517
- Barometric pressure
- 101.33 kPa
- Density ratio vs sea level 20°C
- 1
Quick answer
Air density falls as temperature rises and as altitude increases, which reduces the mass of air a fan delivers.
rho = P / (R x T)
At a glance
| What it does | Air density from temperature, pressure and altitude. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Air temperature, Altitude |
| Main output | Air density |
| Formula | rho = P / (R x T) |
| Cost | Free — no sign-up, no download |
How to use the Air Density Calculator
- 1Enter the air temperature and site altitude.
- 2Read density and the ratio against standard conditions.
- 3Divide standard CFM by the density ratio to size fans at altitude.
Inputs explained
- Air temperature(°C)
- Enter the air temperature in °C.
- Altitude(m)
- Enter the altitude in m.
Worked example
Using the values the calculator loads with:
Inputs
- Air temperature20 °C
- Altitude0 m
Results
- Air density1.2041 kg/m³
- In lb/ft³0.07517
- Barometric pressure101.33 kPa
- Density ratio vs sea level 20°C1
Frequently asked questions
Why does altitude matter for HVAC?
Thinner air carries less heat, so you need more CFM for the same capacity above about 750 m.
Does humidity change it?
Slightly — moist air is a little lighter than dry air at the same temperature.
What do I need to enter into the Air Density Calculator?
Just 2 values: air temperature, altitude. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Air Density Calculator work out the answer?
Air density falls as temperature rises and as altitude increases, which reduces the mass of air a fan delivers. It applies the formula rho = P / (R x T) and shows the working so you can check each step by hand.
Is the Air Density Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.