Density Altitude Calculator
On a 95°F afternoon, a 5,000-ft field performs like 8,300 ft. Enter your numbers manually, or type any US airport to compute density altitude from its live METAR temperature, current altimeter, and surveyed field elevation — the same data that powers 2,100+ ATIS Alerts airport pages.
The airplane performs as if it were at 9,100 ft on a standard day. High density altitude — performance charts are mandatory, expect a long roll and a shallow climb, and consider weight, runway length, and a cooler time of day.
⚠️ Not for operational use. Always verify with official FAA-approved preflight weather sources before flight.
What is density altitude?
Density altitude is pressure altitude corrected for non-standard temperature — in plain English, the altitude your airplane thinks it's at. Air gets less dense as it gets hotter, higher, and lower-pressure, and every part of the airplane cares: the wing makes less lift at a given airspeed, a normally-aspirated engine makes less power, and the propeller gets less bite. The airplane doesn't know the field elevation; it only knows the air it's flying in.
The formula, with a worked example
Step 1 — pressure altitude: PA = field elevation + (29.92 − altimeter) × 1,000. Step 2 — density altitude: DA = PA + 120 × (OAT − ISA temp), where the ISA (standard) temperature is 15°C at sea level, falling 2°C per 1,000 ft.
Worked example — Centennial Airport (KAPA), field elevation 5,885 ft, on a 30°C afternoon with the altimeter at 30.05: PA = 5,885 + (29.92 − 30.05) × 1,000 = 5,755 ft. ISA at 5,755 ft is about 3.5°C, so the deviation is +26.5°C, and DA = 5,755 + 120 × 26.5 ≈ 8,940 ft. A sea-level Cessna 172 that climbs at 700 fpm might manage barely 300 fpm here — with a much longer takeoff roll to go with it.
Pressure altitude vs density altitude
Pressure altitude handles the barometer; density altitude adds the thermometer. Pressure changes a few tenths of an inch between weather systems, but temperature swings 15–20°C in a single summer day — which is why the same runway that felt fine at 8 AM can be marginal at 3 PM. The calculator shows both numbers so you can see which one is doing the damage.
What high density altitude does to your airplane
Three hits compound: the wing needs more true airspeed for the same lift, the engine produces less power in thinner air, and the propeller— a rotating wing — produces less thrust. You'll also lift off at the same indicated airspeed but a higher true airspeed, meaning more ground speed and more runway behind you before you fly. When to worry:
| Density altitude | What it means for a light aircraft |
|---|---|
| Below 3,000 ft | Near sea-level performance for most light aircraft. Normal takeoff planning applies. |
| 3,000 – 6,000 ft | Noticeably longer takeoff roll and weaker climb. Check the POH charts; lean for takeoff where your POH calls for it. |
| 6,000 – 9,000 ft | High. Performance charts are mandatory, weight discipline matters, and morning departures beat hot afternoons. |
| Above 9,000 ft | Many normally-aspirated trainers are marginal here. Know your climb-rate math and your service ceiling — and consider not going. |
Density altitude FAQ
How do I calculate density altitude?
Two steps: pressure altitude = field elevation + (29.92 − altimeter setting) × 1,000. Then density altitude = pressure altitude + 120 × (OAT − ISA temperature), where ISA is 15°C at sea level minus 2°C per 1,000 ft of pressure altitude. This calculator does both steps for you — the same method as an E6B.
Does ATIS announce density altitude?
Often, yes — many towers add a density altitude advisory to the ATIS when it exceeds the field elevation by a significant margin (commonly 1,000 ft or more). If you hear "density altitude 8,500" on a 5,900-ft field, that's the airport telling you performance will be poor.
Does humidity affect density altitude?
Slightly. Humid air is less dense than dry air, so on hot, muggy days the true density altitude runs a few hundred feet higher than the dry-formula number. The E6B and POH charts use the dry formula too, so this calculator matches them — just treat muggy-day numbers as optimistic.
What's the difference between pressure altitude and density altitude?
Pressure altitude corrects your field elevation for non-standard pressure (what your altimeter reads set to 29.92). Density altitude then corrects pressure altitude for non-standard temperature. Performance charts almost always want density altitude, because temperature is what changes most during the day.
Can density altitude be lower than field elevation?
Yes — on cold, high-pressure days. A −20°C morning at a 1,000-ft field can produce a density altitude well below sea level, which is why winter performance feels so crisp.
About this data
Airport mode uses the current METAR temperature and altimeter from the FAA/NWS Aviation Weather Center (aviationweather.gov, refreshed roughly every minute) and surveyed field elevations from the public OurAirports dataset. The math follows the E6B / FAA Pilot's Handbook (dry) convention. Built by ATIS Alerts, a product of The Better Travelers, LLC.
Add live density altitude for your airport to your website
Mountain and high-desert flight schools: show your field's current density altitude right on your site. It reads the live METAR temperature and altimeter against your surveyed field elevation, tones the number green/amber/red, and refreshes itself — one copy-paste line, free.
Showing: KAPA · Centennial Airport
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