If you need a quick way to estimate altitude from barometric pressure, this altitude calculator gives you instant results in both meters and feet. It also estimates pressure altitude and density altitude, which are especially useful in aviation, mountain planning, and weather analysis.
Free Altitude Calculator
Enter local pressure, sea-level pressure, and optional air temperature to calculate altitude values.
What this altitude calculator measures
This tool calculates three related values:
- Barometric altitude: altitude estimated from your station pressure and your selected sea-level reference pressure.
- Pressure altitude: altitude referenced to standard sea-level pressure (1013.25 hPa / 29.92 inHg).
- Density altitude: pressure altitude corrected by temperature, showing how “thin” the air behaves.
How the calculations work
1) Barometric altitude equation
For the troposphere and standard atmosphere assumptions, altitude can be estimated with:
Where:
- h = altitude in meters
- P = measured station pressure
- P0 = sea-level reference pressure
2) Pressure altitude
Pressure altitude uses the same formula but forces sea-level reference to 1013.25 hPa. This is useful in aviation because it normalizes conditions and supports standard performance comparisons.
3) Density altitude estimate
Density altitude is estimated using a common pilot approximation:
where ISA temperature is approximated as:
How to use this tool correctly
- Select the pressure unit (hPa or inHg).
- Enter your measured station pressure.
- Enter local sea-level pressure (QNH) for barometric altitude.
- Optionally enter ambient air temperature for density altitude.
- Click Calculate Altitude.
Example use case
Imagine your station pressure is 850 hPa and local sea-level pressure is 1012 hPa on a warm day (30°C). The calculator can show that your pressure-based altitude is substantial, and your density altitude may be much higher due to temperature. That means reduced engine performance, less lift, and longer takeoff distance for aircraft.
Why altitude and density altitude matter
- Aviation: takeoff/landing performance, climb rate, and safety margins.
- Hiking and mountaineering: oxygen availability and exertion planning.
- Meteorology: interpreting pressure fields and weather behavior.
- Engineering and science: calibrating instruments and environmental models.
Limitations
This calculator provides practical estimates, not certified navigation values. Real atmosphere conditions vary by humidity, temperature profile, and local weather dynamics. Always use certified instruments and official guidance when safety is involved.
Altitude calculator FAQ
Is this the same as GPS altitude?
No. GPS altitude is geometric (satellite-based), while this calculator uses barometric pressure. Both can differ significantly.
What if station pressure is higher than sea-level pressure?
The result may become negative altitude, which is physically possible in below-sea-level locations.
Can I use inHg values directly?
Yes. Choose inHg in the dropdown and enter both pressure values in inHg; the calculator converts internally.
Final thoughts
A reliable altitude estimate starts with good pressure data. Use this calculator as a fast planning tool for travel, weather interpretation, and flight prep. For operational decisions, always verify with local official data and calibrated instruments.