Altitude & Depth Converter

Altitude and depth conversion involves translating measurements of vertical position above or below a reference point — typically sea level — between different unit systems. Whether you are calculating how high an aircraft is flying, how deep a diver has descended, or how tall a mountain stands, accurate unit conversion is essential.

Altitude refers to height above sea level and is critical in aviation, meteorology, mountaineering, and telecommunications. Pilots use flight levels (where FL350 means 35,000 feet), hikers track elevation gain in meters or feet, and engineers account for atmospheric pressure changes at different heights. Depth, on the other hand, measures how far below the surface something is — vital for diving, oceanography, and underwater construction.

This converter handles a wide range of length-based units — meters, kilometers, feet, yards, miles, fathoms, nautical miles, flight levels, and pressure-based depth units. It also calculates atmospheric pressure at altitude and water pressure at depth, making it a comprehensive tool for anyone working with vertical measurements.

The calculator uses meters as the common intermediate unit. All conversions first convert the input value to meters, then convert from meters to the target unit. For altitude mode, the barometric formula approximates how air pressure decreases with height.

As altitude increases, atmospheric pressure decreases because there is less air above pressing down. The calculator uses the barometric formula: P = e^(-h/8500), where h is the height in meters. This is an approximation of the International Standard Atmosphere (ISA) model.

At sea level, standard atmospheric pressure is 101.325 kPa (1 atm). At the cruising altitude of a commercial aircraft (about 10,668 meters or 35,000 feet), the outside air pressure drops to roughly 23% of its sea-level value. This is why aircraft cabins must be pressurized. The temperature also decreases with altitude at a standard lapse rate of about 6.5°C per 1,000 meters in the troposphere.

Understanding pressure changes at altitude is crucial for pilots, mountaineers, weather forecasters, and anyone designing equipment that operates across different elevations.

Underwater, pressure increases by approximately 1 atmosphere for every 10 meters of depth. This means at 30 meters, a diver experiences about 4 atmospheres of absolute pressure — one from the air above the water plus three from the water column. The calculator computes pressure in atmospheres, bars, and PSI.

This information is vital for scuba divers, who must manage nitrogen absorption at different pressures, submarine engineers designing hulls to withstand immense deep-sea pressures, and marine scientists studying organisms that live at extreme depths. The Mariana Trench, at nearly 11,000 meters deep, experiences pressures exceeding 1,000 atmospheres.

Follow these steps to convert altitude or depth measurements:

1. Enter the value: Type your measurement into the value field. For example, enter 35000 for a typical commercial flight altitude.
2. Select the source unit: Choose from meters, kilometers, feet, yards, miles, fathoms, nautical miles, flight levels, or pressure-based units.
3. Select the target unit: Choose the unit you want to convert to.
4. Choose Altitude or Depth: Toggle between altitude mode (for positive elevations above sea level) and depth mode (for measurements below the surface). Depth mode activates the pressure-at-depth calculations.
5. Read the results: The main result shows the converted value. Below that, you see the equivalent in meters, feet, kilometers, and flight levels. In altitude mode, air pressure and temperature information appear. In depth mode, pressure readings in atm, bar, and PSI are shown.
6. Check reference landmarks: Compare your value against known landmarks like the Dead Sea, Mount Everest, and the Mariana Trench to contextualize the measurement.

In aviation, altitude is measured in feet for vertical separation between aircraft. Flight levels like FL350 (35,000 feet) ensure safe spacing. Pilots and air traffic controllers must convert between feet and meters when operating in different regions, as some countries use metric altitude references.

Scuba diving relies heavily on depth measurements. Recreational divers are limited to 40 meters (130 feet), while technical divers may descend to 100 meters or beyond. Accurate depth conversion helps divers plan decompression stops and manage nitrogen narcosis risk. Pressure readings in bar and PSI are essential for monitoring tank pressure and calculating gas consumption.

Mountaineers track elevation in meters to plan acclimatization schedules. At high altitudes above 2,500 meters, the risk of altitude sickness increases significantly. Knowing the exact altitude helps climbers pace their ascent and recognize dangerous elevations. Mountain weather stations report conditions in both metric and imperial units.