When is density altitude equal to pressure altitude?

Density altitude is equal to pressure altitude specifically when the atmospheric conditions are standard, meaning that the temperature is at sea level standard (15°C or 59°F) and the pressure is also at standard atmospheric conditions (29.92 inHg or 1013.25 hPa). In such standard conditions, the definitions of density altitude and pressure altitude align perfectly, leading to an equal measurement.

When atmospheric conditions deviate from these standards—such as when temperatures are higher or lower than standard—density altitude will not equal pressure altitude. This is due to the influence of temperature on air density; warmer air is less dense, which raises density altitude, while cooler air is denser, lowering density altitude. Therefore, it is at these standard conditions that the two altitudes match, highlighting the importance of temperature and pressure in aviation calculations.