Aviation unit converter
Convert the units pilots and controllers use: speed, pressure, length and distance, and temperature, with every unit shown at once.
Runs entirely in your browser
In every unit
| Unit | Value |
|---|
Exact defined factors; results are rounded to the number of significant figures you choose (8 by default). Mach uses 340.294 m/s, the speed of sound at ISA sea level. Not for flight planning or navigation.
How to convert aviation units
- Pick what you are converting: speed, pressure, length and distance, or temperature.
- Type a value and choose the units to convert from and to. You can type in either box.
- Read the result and the formula, or look down the table for the same value in every unit.
How the conversions work
Each category has a base unit: metres per second for speed, pascals for pressure and metres for length. A value is multiplied by the size of its unit in the base unit and divided by the size of the target unit. All factors are exact definitions: 1 knot = 1,852/3,600 m/s, 1 mph = 1,609.344/3,600 m/s, 1 foot = 0.3048 m, 1 nautical mile = 1,852 m, 1 statute mile = 1,609.344 m, 1 hPa = 100 Pa, 1 mmHg = 133.322387415 Pa and 1 inHg = 25.4 mmHg = 3,386.38864 Pa (the conventional values used in ICAO Annex 5 and NIST Special Publication 811).
Temperature has different zero points, so it is converted through kelvin: K = °C + 273.15 and °F = °C × 9/5 + 32. The unit list follows ICAO Annex 5 (Units of Measurement to be Used in Air and Ground Operations), in which pressure is in hectopascals, altitude in feet or metres and speed in knots or km/h. Not for flight planning or navigation.
Questions
How do I convert knots to km/h?
Multiply by 1.852, because one knot is one nautical mile per hour and a nautical mile is exactly 1,852 metres. So 100 knots is 185.2 km/h, or about 115 mph.
How do I convert hPa to inHg?
Divide hectopascals by 33.8639 to get inches of mercury. The standard sea-level pressure of 1013.25 hPa is 29.9213 inHg, so a QNH of 1013 is about 29.91 inHg. Millibars (mb) and hectopascals are the same unit.
What is the difference between a nautical mile and a statute mile?
A nautical mile is exactly 1,852 m (about 1.1508 statute miles) and is related to one minute of latitude. A statute mile is 1,609.344 m. Aviation distances outside the US, and all speeds in knots, use nautical miles.
Why is Mach not a fixed speed?
Mach is a ratio to the local speed of sound, which falls with temperature. This tool uses the ISA sea-level value of 340.294 m/s (about 661.5 knots), so it is only a reference. At airliner cruise altitudes Mach 1 is closer to 573 knots.
What does feet per minute mean?
It is the unit of vertical speed: 500 ft/min is about 2.54 m/s. It is included in the speed list so that climb and descent rates can be converted.
Are the conversions exact?
The factors are exact definitions (for example 1 ft = 0.3048 m, 1 NM = 1,852 m, 1 inHg = 3,386.38864 Pa and 1 mmHg = 133.322387415 Pa), so any rounding is only in the last digit shown.