Atmospheric Pressure vs Elevation Calculator

An atmospheric pressure vs elevation calculator estimates air pressure at a chosen height above sea level using a standard-atmosphere model. Enter elevation in metres and the calculator returns estimated pressure in kilopascals, with equivalent hectopascals and sea-level pressure ratio for context.

Formula

The calculator uses the standard-atmosphere pressure equation for the lower atmosphere:

p = p₀ × (1 − Lh / T₀)^5.25588

• p is estimated atmospheric pressure at elevation, in kilopascals (kPa).
• p₀ is standard sea-level pressure, 101.325 kPa.
• L is the standard temperature lapse rate, 0.0065 kelvin per metre (K/m).
• h is elevation above standard sea level, in metres (m).
• T₀ is standard sea-level temperature, 288.15 K.

The exponent is derived from the standard-atmosphere constants. The other outputs convert the pressure to hectopascals and express it as a percentage of standard sea-level pressure. One kPa equals 10 hPa; one hPa is numerically equal to one millibar.

Worked Example

With the default elevation of 1,000 m:

1. Calculate the temperature factor: 1 − (0.0065 × 1,000 / 288.15) ≈ 0.97744.
2. Raise it to the stated exponent: 0.97744^5.25588 ≈ 0.88699.
3. Multiply by standard sea-level pressure: 101.325 × 0.88699 ≈ 89.87 kPa.
4. Convert to hectopascals: 89.87 × 10 ≈ 898.7 hPa. Relative to sea level, that is about 88.7%.

These are model estimates, rounded to match the calculator outputs, not a reading from a local weather station.

How Elevation Changes Air Pressure

Air has weight, so the atmosphere above a location exerts pressure on the air below it. As elevation increases, less air lies overhead and pressure generally falls. The relationship is nonlinear: pressure does not decrease by the same number of kilopascals for every kilometre gained. Near sea level, a given vertical rise produces a larger pressure change than the same rise much higher in the atmosphere.

Pressure is force per unit area. Meteorological reports commonly use hectopascals (hPa) or millibars (mbar); scientific and engineering contexts often use pascals (Pa) or kilopascals. In US customary units, pressure may be given in inches of mercury (inHg) or pounds per square inch (psi). For comparison, 101.325 kPa is approximately 14.696 psi or 29.92 inHg at standard sea-level conditions.

When to Use This Estimate

This calculation is useful for understanding how altitude affects a standard pressure value, comparing approximate conditions at different elevations, or checking the scale of a pressure change. For example, the default 1,000 m result is roughly 89% of standard sea-level pressure. It can also help explain why weather instruments and aircraft systems distinguish pressure at a location from pressure adjusted to sea level.

Use elevation above mean sea level, not height above the ground at your location. If a building is 30 m tall on terrain at 1,000 m elevation, the roof is approximately 1,030 m above sea level. The calculator accepts metres; convert feet by multiplying by 0.3048. For instance, 5,000 ft is 1,524 m.

Standard Model vs Local Weather Pressure

The calculator assumes a standard atmosphere: a defined sea-level temperature and a fixed temperature decrease with altitude through the lower atmospheric layer. Real air is affected by weather, latitude, season, time of day, and the temperature profile above a site. Consequently, actual station pressure can be higher or lower than the estimate at the same elevation.

There are also two pressure figures that are easily confused. Station pressure is the pressure measured at the instrument’s elevation. Sea-level pressure is a value adjusted to allow weather comparisons between places at different elevations. A reported sea-level pressure is not necessarily the pressure physically measured at a mountain station. If you need current local conditions, consult a suitably located weather station or calibrated instrument rather than treating this standard-atmosphere result as an observation.

Limits and Common Mistakes

• Entering feet as metres: this makes the computed elevation about 3.28 times too large. Convert units before entering a value.
• Using height above ground: the formula needs elevation above sea level. Add the terrain elevation when calculating a rooftop or other raised point.
• Expecting exact weather pressure: the standard atmosphere is a reference model, not a forecast or live measurement.
• Assuming the formula works at any altitude: this simplified equation represents the tropospheric lapse-rate layer, conventionally up to about 11 km in the standard atmosphere. The calculator’s 20,000 m input ceiling is a mathematical allowance, not a claim that this equation remains physically appropriate throughout that range.
• Comparing unlike pressure conventions: check whether a value is station pressure or sea-level adjusted pressure and whether its unit is hPa, inHg, or another unit.

For elevations above the lower-atmosphere layer, a more complete standard-atmosphere model uses separate temperature layers and equations. For precise work, use the appropriate atmospheric model and verified local inputs. Atmospheric pressure also varies over time, so extra decimal places do not make a standard estimate more accurate.

Frequently Asked Questions

How much does atmospheric pressure decrease with elevation?
There is no fixed decrease per metre because pressure falls nonlinearly. Near sea level, the change is comparatively rapid; at higher elevations, the same vertical distance generally corresponds to a smaller pressure change.

What is atmospheric pressure at 1,000 metres?
The standard-atmosphere estimate is about 89.9 kPa, or 899 hPa. Actual pressure depends on weather and local atmospheric conditions.

Is 1,000 hPa the same as 1,000 mbar?
Yes. One hectopascal equals one millibar, so the numerical values are identical.

Does this calculator show the pressure I would measure outdoors?
No. It estimates pressure from elevation under standard-atmosphere assumptions. A local instrument reading can differ because of weather and temperature.

Can I enter elevation in feet?
Convert feet to metres first by multiplying by 0.3048. The calculator’s elevation input is in metres.

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in h | Elevation | m | 1000 | 0 | 20000
out p | Atmospheric pressure | kPa | 101.325 * (1 - 0.0065 * h / 288.15) ^ 5.25588 | 2
out q | Atmospheric pressure | hPa | p * 10 | 1
out r | Sea-level pressure ratio | % | p / 101.325 * 100 | 1