A basic environmental planning calculator for understanding air-density effects on UAS performance.
Start here
- Enter site elevation, QNH pressure and outside air temperature in the shown units.
- Choose Calculate to compare those conditions with the standard atmosphere.
- Read pressure altitude, density altitude and air-density ratio.
How to read the results
Higher density altitude means less dense air. Apply aircraft performance data separately; this tool does not calculate aircraft-specific derating.
Optional aircraft profile: Manual values
Air Density and Density Altitude Calculator
Planning output only. Verify assumptions and results against authoritative data, manufacturer information, approved procedures, test evidence and competent engineering or regulatory review before use.
Calculation basis
Pressure altitude is estimated from site elevation and QNH. Standard-atmosphere pressure at that pressure altitude is combined with the entered dry-air temperature to estimate density. Density altitude is the ISA altitude with the same density.
Limitations and verification
- Humidity is not included; high moisture content lowers density further.
- Uses a standard-troposphere model and is intended for planning, not certified performance computation.
- Use current official weather, manufacturer performance data and approved limits for operations.
Version and review status
Formula set: v1.2
Staging review date: 17 August 2026
Status: Staging beta pending user acceptance and cross-browser checks.
Using this calculator
A basic environmental planning calculator for understanding air-density effects on UAS performance.
Inputs and units
| Input | Unit or format |
|---|---|
| Site elevation | ft AMSL |
| QNH / altimeter setting | hPa |
| Outside air temperature | °C |
Model and formula
Pressure altitude (ft) = elevation + (1013.25 − QNH) × 27. Standard pressure uses p = 101325 × (1 − 0.0065h / 288.15)^(9.80665 / [287.05287 × 0.0065]), with h in metres. Dry density = p / [287.05287 × (OAT + 273.15)]. Density altitude inverts this standard-atmosphere density relationship.
Worked example
At 0 ft elevation, QNH 1,013.25 hPa and 15 °C, the calculation gives pressure altitude 0 ft, dry-air density 1.2250 kg/m³, density ratio 100.0% and density altitude approximately 0 ft. Raising temperature to 30 °C with the same elevation and QNH gives density altitude about 1,724 ft.
Interpreting the result
Density altitude expresses the entered density as an equivalent ISA altitude. It is not an allowable payload, take-off distance or flight-time prediction. Use the aircraft manufacturer’s performance method for the actual configuration and conditions.
Limits and verification
- Humidity is not included; high moisture content lowers density further.
- Uses a standard-troposphere model and is intended for planning, not certified performance computation.
- Pressure altitude and density altitude must each be at or below 11,000 m (approximately 36,089 ft); conditions above this model boundary are rejected.
- Use current official weather, manufacturer performance data and approved limits for operations.
Worked examples checked against the calculator source on . These are reproducible calculation checks, not aircraft trials, site measurements or operational approval. Existing formula versions and technical review status remain as stated above.