Pressure Altitude Calculator
Pressure altitude from field elevation and altimeter setting in inHg or hPa, plus an approximate density altitude when you add the outside air temperature. How it works
Use the Pressure Altitude Calculator
About the Pressure Altitude Calculator
Pressure altitude is the field elevation plus 1,000 ft for every inch of mercury the altimeter setting is below 29.92. At a 5,000 ft field with a setting of 30.12 inHg it is 4,800 ft. Add the outside air temperature and the page also shows an approximate density altitude: 8,000 ft at a 5,000 ft field with 29.92 inHg and 30 °C.
Pressure altitude by altimeter setting
| Altimeter setting (inHg) | Field at 0 ft | Field at 1,000 ft | Field at 5,000 ft |
|---|---|---|---|
| 29.42 | 500 ft | 1,500 ft | 5,500 ft |
| 29.62 | 300 ft | 1,300 ft | 5,300 ft |
| 29.92 | 0 ft | 1,000 ft | 5,000 ft |
| 30.12 | -200 ft | 800 ft | 4,800 ft |
| 30.42 | -500 ft | 500 ft | 4,500 ft |
Each 0.01 inHg below 29.92 adds 10 ft. A setting above 29.92 lowers the pressure altitude.
Density altitude at a 5,000 ft field with a 29.92 inHg setting
| Outside air temperature | Standard temperature at 5,000 ft | Difference from standard | Density altitude |
|---|---|---|---|
| 0 °C (32 °F) | 5 °C | -5 °C | 4,400 ft |
| 10 °C (50 °F) | 5 °C | 5 °C | 5,600 ft |
| 20 °C (68 °F) | 5 °C | 15 °C | 6,800 ft |
| 30 °C (86 °F) | 5 °C | 25 °C | 8,000 ft |
| 40 °C (104 °F) | 5 °C | 35 °C | 9,200 ft |
Each degree Celsius above standard adds 120 ft, the page’s approximation. At 5 °C the density altitude equals the pressure altitude.
This page against the FAA correction table, for a sea-level field
| Altimeter setting (inHg) | This page | FAA Pilot’s Handbook, Figure 11-3 |
|---|---|---|
| 28.0 | 1,920 ft | 1,824 ft |
| 29.0 | 920 ft | 863 ft |
| 29.7 | 220 ft | 205 ft |
| 30.1 | -180 ft | -165 ft |
| 31.0 | -1,080 ft | -983 ft |
The first column of figures is what this page returns. The FAA column is copied from the handbook’s table.
How to use this tool
- Type the altimeter setting in inHg (28.00 to 31.00) or choose hPa (948 to 1,050). The page starts at the standard 29.92 inHg.
- Type the field elevation and choose feet or meters. The range is −1,000 to 45,000 ft.
- Optionally type the outside air temperature and choose °C or °F, from −90 to 60 °C. Without it the page shows pressure altitude only.
- Read the pressure altitude, the approximate density altitude and how far the setting is from standard.
Frequently asked questions
- How do you calculate pressure altitude from the altimeter setting?
- Add (29.92 − altimeter setting) × 1,000 ft to the field elevation. At a 1,000 ft field with a setting of 29.62 inHg that is 1,000 + 0.30 × 1,000 = 1,300 ft. A setting above 29.92 gives a smaller number: 30.12 inHg at the same field is 800 ft.
- What is the difference between pressure altitude and density altitude?
- Pressure altitude is the altitude the altimeter shows when it is set to 29.92 inHg. The FAA defines density altitude as pressure altitude corrected for nonstandard temperature, and says aircraft perform as though they were at the density altitude. When the temperature is standard the two are equal, as at 5 °C at 5,000 ft; at 30 °C the same field has a density altitude of 8,000 ft.
- How is density altitude calculated on this page?
- It finds the standard temperature at the pressure altitude, 15 °C minus 2 °C per 1,000 ft (never below −56.5 °C), and adds 120 ft for each degree Celsius the outside air is above it. At sea level and 30 °C that is 15 °C above standard, so 1,800 ft. The 120 ft per degree step is the rule of thumb pilots are taught (Plane & Pilot lists it among its top ten), not an exact formula, which is why the result is labeled approximate; humidity is not used.
- Is the 1,000 ft per inHg rule accurate?
- It is the FAA’s rule of thumb: the Aeronautical Information Manual says an error of one inch in the altimeter setting equals 1,000 ft of altitude. The correction table in the FAA’s Pilot’s Handbook of Aeronautical Knowledge is slightly smaller, for example 1,824 ft at 28.0 inHg against 1,920 ft here. Across 28.0 to 31.0 inHg the two differ by up to 97 ft at a sea-level field.
- Can I enter meters, °F or hPa?
- Yes: choose the unit next to the field. 1,000 m is converted to 3,280.84 ft. A setting in hPa is measured from the standard 1,013.25 hPa and divided by 33.86389, the conventional inch of mercury in hectopascals, so 1,000 hPa gives a pressure altitude of 391 ft at a sea-level field and 1,013.25 hPa gives 0 ft. Changing the unit converts the number already typed, so the result stays put. The page refuses a setting outside 28.00 to 31.00 inHg or 948 to 1,050 hPa rather than guessing.
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