Altitude Converter

Altitude is measured in different units depending on the context.

Basic conversions:

• 1 foot = 0.3048 meters (exact)
• 1 meter = 3.28084 feet
• 1 kilometer = 3,280.84 feet

Flight Levels (FL): Flight levels are used in aviation above the transition altitude.

• Flight Level = altitude in feet / 100
• FL350 = 35,000 feet = 10,668 meters
• FL100 = 10,000 feet = 3,048 meters

Approximate pressure at altitude (standard atmosphere):

Pressure altitude formula (ISA standard):

• Pressure (hPa) ≈ 1013.25 × (1 − altitude_m × 0.0000226)**5.256

Aviation worldwide uses feet for altitude, except in China and some CIS countries which use meters.

The flight-level system is the clever bit worth understanding. Below a transition altitude every aircraft sets its altimeter to the local sea-level pressure to read true height, but above it everyone switches to the same standard setting of 1013.25 hPa and reports “flight levels” instead. The altitudes are no longer strictly true, but because every plane uses the identical reference, they all read consistently relative to each other, which is what keeps them safely stacked even as real atmospheric pressure rolls across the country.

That’s also why a barometric altimeter and your phone’s GPS altitude rarely agree. The altimeter infers height from air pressure, which shifts with the weather, so a passing low-pressure system makes it read high unless you reset it; GPS measures geometric height directly and ignores pressure entirely. The thinning of the air is the other thing the numbers hide: pressure roughly halves by 18,000 feet, which is why climbers gasp on high peaks and why airliner cabins are pressurized to feel like a comfortable 6,000 to 8,000 feet rather than the 35,000 outside.