About this tool
Density Altitude Calculator is a free, in-browser tool that works out the density altitude at an airfield from three inputs pilots always have: field elevation, the altimeter setting (in inches of mercury or hectopascals), and the outside air temperature in °C or °F. Everything is computed locally as you type — nothing is uploaded.
It follows the standard rule-of-thumb chain. Pressure altitude is PA = elevation + (29.92 − altimeter_inHg) × 1000. The standard-atmosphere (ISA) temperature at that pressure altitude is ISA = 15 − 1.98 × (PA ÷ 1000) °C. Density altitude then corrects for how far the actual temperature sits above standard: DA = PA + 118.8 × (OAT − ISA), with OAT converted to °C first. The tool also shows the ISA temperature and your ISA deviation.
Density altitude is the altitude the air 'feels like' to your wing, propeller and engine: on a hot, high day it can be thousands of feet above the field elevation, lengthening the takeoff roll and flattening the climb. Use it for a quick pre-flight performance check, but treat the result as an estimate — it is not for real-world navigation and must be verified against your aircraft's performance charts and official sources.