Aviation temperature conversions
Aviation weather and performance work commonly uses degrees Celsius, while many everyday U.S. references use Fahrenheit. Engineering equations may require Kelvin. Converting the unit correctly is especially important for density altitude, true airspeed and speed-of-sound calculations.
Celsius to Fahrenheit
Use °F = (°C × 9/5) + 32. For example, 20°C becomes 68°F. Freezing is 0°C or 32°F, which is a useful mental check.
Fahrenheit to Celsius
Use °C = (°F − 32) × 5/9. A temperature of 86°F becomes 30°C.
Celsius and Kelvin
Kelvin uses the same size degree as Celsius but starts at absolute zero. K = °C + 273.15. A temperature of 15°C is 288.15 K. Kelvin is often required in physics equations because it is an absolute temperature scale.
Why aviation often uses Celsius
METAR temperature and dew point are reported in Celsius, and standard-atmosphere relationships are commonly expressed in Celsius. Aircraft performance charts may use Celsius even when other aircraft instruments display Fahrenheit.
Do not convert temperature differences like absolute temperatures
A change of 1°C equals a change of 1 K and equals a change of 1.8°F. When dealing with a temperature difference rather than an actual temperature, the +32 offset does not apply in the same way.
Check the chart label
Before entering temperature into a calculator or POH chart, verify whether the source expects °C or °F. Entering 30°F as though it were 30°C creates a major performance error.
Related PilotDesk guides
Density altitude · ISA temperature · Mach and speed of sound