Density Altitude & Air Density

Air density, density altitude and dyno correction, straight from your iPhone's barometer. The best tool for engine tuning, ballistics, aviation and golf.

Air density, density altitude (DA) and relative air density (RAD), computed with the precision that tuning an engine or planning a takeoff actually needs.

WHAT IT CALCULATES

• Air density (kg/m³, lb/ft³, lb/gal US) • Density altitude • Relative air density (RAD) • Relative horsepower • Dyno correction factor • Dew point • Virtual temperature • Altimeter setting (QNH) • Actual station pressure

WHO IT'S FOR

Jetting and carburetion. Size your jets on a kart, bike, scooter or race car for the conditions you actually have today, and build proper jetting charts instead of guessing.

Dyno testing. Apply the correction factor to compare runs from different days and know how much of the difference was the engine and how much was the air density.

Drag racing. Density altitude and RAD for the run, before you stage.

Aviation and RC flying. Density altitude and altimeter setting for takeoff performance. For model aircraft, the right nitro mix for the day's conditions.

Precision shooting. Track air density through the day and adjust your loads as conditions move.

Golf. How far the ball actually carries in today's conditions.

LOG THE DAY

Record a session and see how conditions change through the day on a chart, with the change since the first reading. Export it as CSV and cross it with your dyno sheet or your load book.

POWER CORRECTION

Pick the standard your dyno sheet uses: SAE J1349, SAE J607, DIN 70020 or ECE R85.

WHERE THE DATA COMES FROM

Three sources, and you always know which one you are on. Read the barometer built into your iPhone for the real pressure right where you stand. Pull temperature, pressure and humidity from the nearest weather station, with its name and distance always in view. Or type it all in by hand. Apart from the station lookup, the app needs no connection.

ACCURACY

Density is solved with the full CIPM/Picard equation, including the compressibility factor and water vapour pressure. This is not an ideal-gas approximation: it's the formula used in metrology.

UNITS

Pressure in mb, hPa, mmHg or inHg. Temperature in ºC or ºF. Altitude in metres or feet. Density in kg/m³, lb/ft³, lb/gal (US) or gr/ft³ for precision shooting.

PRIVACY

The app collects nothing. Your readings, sessions and settings stay on your device. There is no analytics, no third-party SDK and no account. The only network request is the weather station lookup, sent over a secure connection with coordinates rounded to about 110 m and no identifier attached.

Available in English, Spanish, German, French, Italian, Portuguese, Russian, Japanese, Polish and Dutch.