UtilityGlen

Atmospheric Pressure Converter

Convert barometric pressure instantly between hectopascals, millibars, inches of mercury, millimeters of mercury, pascals, kilopascals, atmospheres and psi.

Barometer lab • Eight precision units

Understand the atmosphere, one unit at a time.

Live two-way pressure conversion, weather references, and a complete measurement dashboard.

Local browser calculation

Live pressure conversion

Two editable fields
Live pressure equation

Enter a pressure to calculate the equivalent.

Explore barometer reference values

The Barometer Expedition

There's an ocean above your head. It's made of air.

We live at the bottom of a vast atmosphere. Every moment, the air above us exerts pressure on the world below.

Weather maps call it barometric pressure. A home weather station might report 1013 hPa. An American forecast might show 29.92 inHg. A physics textbook might express the same reference pressure as 101,325 Pa.

Different measurements. The same physical pressure.

The free UtilityGlen Atmospheric Pressure Converter instantly translates between eight pressure units, helping you understand barometers, weather forecasts, scientific equations and engineering measurements.

Eight pressure units Two-way conversion Weather references
Observatory instrument 001 Barometer
Atmospheric pressure observatory illustration A large illuminated circular barometer with pressure markings, a needle and atmospheric clouds over a mountain landscape. LOW HIGH BAROMETRIC 1013.25 hPa • STANDARD ATM THE WEIGHT OF THE SKY
Hectopascals
1013.25
hPa
Inches of mercury
29.92
inHg

Illustrated standard atmosphere. Actual pressure changes with location and weather.

The big idea

Atmospheric pressure is force divided by area.

The atmosphere has mass. Gravity gives that air weight, producing pressure at Earth's surface. A pressure converter changes the unit used to express the measurement—not the pressure itself.

DISCOVERY 01 / Decoding the atmosphere

What is an Atmospheric Pressure Converter?

An atmospheric pressure converter is a unit-conversion tool that translates a pressure value between different measurement systems. You may also see it called a barometric pressure converter.

Atmospheric pressure appears in weather reports, barometer readings, marine forecasts, aviation references, scientific experiments and engineering calculations. Different countries and industries prefer different units.

UtilityGlen allows you to convert between hPa, mb, inHg, mmHg, Pa, kPa, atm, and psi.

Type a pressure in either editable field, choose your units, and see an instant conversion. The tool also displays all eight equivalents together, provides useful example presets, and explains the selected conversion formula.

Eight units. One atmosphere.

Think of these as eight different languages for describing the same pressure.

hPa

Hectopascal

One hectopascal equals 100 pascals. Widely used in meteorology.

mb

Millibar

Numerically identical to hPa: one millibar is exactly one hectopascal.

inHg

Inch of mercury

Traditionally associated with mercury barometers and US weather reports.

mmHg

Millimeter of mercury

A non-SI pressure unit commonly encountered in historical and technical references.

Pa

Pascal

The SI unit of pressure, equal to one newton per square meter.

kPa

Kilopascal

One kilopascal equals 1,000 pascals. Useful for compact scientific values.

atm

Standard atmosphere

A defined pressure equal to exactly 101,325 pascals.

psi

Pound-force per square inch

Used in engineering and equipment-pressure specifications.

DISCOVERY 02 / Your observatory controls

How to use the Atmospheric Pressure Converter

No equations or manual reference charts needed. Convert pressure in four simple steps.

01

Enter a pressure value

Type a nonnegative absolute pressure in either editable number field.

02

Select your pressure units

Choose any two of the eight supported units—or swap them instantly.

03

See all eight equivalents

Read the converted result, formula, and complete pressure-unit dashboard.

04

Explore reference pressures

Try the standard atmosphere, low-pressure, high-pressure or 950 hPa preset. Copy or reset your results.

Remember: This converter doesn't measure live weather or know your current location. You provide the pressure reading; the tool converts its units.

DISCOVERY 03 / The universal pressure reference

What is standard atmospheric pressure?

One standard atmosphere is a precisely defined reference pressure. It's useful because measurements in different units can be compared against the same baseline.

Defined standard atmosphere

101,325 Pa
Exactly one standard atmosphere

Hectopascals

1013.25 hPa

Millibars

1013.25 mb

Inches of mercury

29.9213 inHg

Pounds per square inch

14.6959 psi

Kilopascals

101.325 kPa

Millimeters of mercury

≈ 760 mmHg

Standard atmospheres

1 atm

Pascals

101,325 Pa

A crucial distinction: Standard atmosphere is a defined reference value. Real atmospheric pressure at sea level isn't always 1013.25 hPa. Weather systems and environmental conditions cause it to vary.

DISCOVERY 04 / Read the atmosphere

Does air pressure tell us what the weather will do?

Atmospheric pressure is one of meteorology's most useful measurements. Broad low-pressure and high-pressure systems are connected to large-scale air movement and changing weather patterns.

But here's where many simple weather explanations go wrong: one pressure value cannot reliably predict tomorrow's weather. Pressure trends, nearby weather systems, elevation and official forecasts all matter.

Lower pressure systems

Low-pressure systems are often associated with rising air, cloud development and unsettled weather. Whether precipitation occurs depends on additional atmospheric conditions.

Tool example preset

980 hPa

An illustrative lower-pressure reference

Higher pressure systems

High-pressure systems frequently involve sinking air and may favor more settled weather, but they do not guarantee clear skies or pleasant conditions.

Tool example preset

1035 hPa

An illustrative higher-pressure reference

Why does pressure decrease with altitude?

As you climb higher, there's generally less air above you. That reduces atmospheric pressure. This is why pressure measured at a mountain station is usually lower than pressure at a nearby sea-level location under otherwise comparable conditions.

Weather services often adjust station measurements to a common sea-level reference so pressure maps can compare observations at different elevations.

DISCOVERY 05 / The calculation laboratory

Atmospheric pressure conversion formulas

Pressure-unit conversion relies on fixed mathematical relationships. The easiest general method is to convert the original measurement to pascals, then convert the pascal value into the target unit.

Universal conversion method

Target value = Source value × (Source factor ÷ Target factor)

Conversion factors represent pascals per unit.

hPa to inHg
inHg = hPa ÷ 33.8638867

Example: 1013.25 hPa is approximately 29.9213 inHg.

inHg to hPa
hPa = inHg × 33.8638867

Example: 30 inHg is approximately 1015.92 hPa.

hPa to millibars
1 hPa = 1 mb

Both units have the same numerical value. For example, 985 hPa = 985 mb.

kPa to hPa
hPa = kPa × 10

Example: 101.325 kPa equals 1013.25 hPa.

hPa to mmHg
mmHg ≈ hPa × 0.7500616

Example: 1000 hPa equals approximately 750.06 mmHg.

atm to psi
psi ≈ atm × 14.69595

Example: 1 atm equals approximately 14.69595 psi.

What about inches and millimeters of mercury?

Mercury-column pressure units have conventional reference definitions. UtilityGlen uses conventional inHg and mmHg conversion factors; other reference temperatures or technical conventions can produce slightly different values.

DISCOVERY 06 / Observatory reference table

Barometric pressure conversion chart

Use this quick-reference table to compare common atmospheric pressure readings in hectopascals, millibars, inches of mercury and kilopascals.

Pressure equivalents

inHg rounded to 2 decimals
Conversion chart for atmospheric pressure in hPa, mb, inHg and kPa
hPa mb inHg kPa
950 950 28.05 95
980 980 28.94 98
1000 1000 29.53 100
1013.25 1013.25 29.92 101.325
1020 1020 30.12 102
1040 1040 30.71 104

These values are reference conversions, not weather observations or universal pressure thresholds.

DISCOVERY 07 / Where pressure matters

Who uses atmospheric pressure conversions?

Pressure conversion connects the worlds of weather forecasting, laboratory science, aviation, marine navigation and engineering.

Weather forecasts and barometers

Compare a home barometer displaying inHg with a weather report showing hPa or mb.

Aviation pressure references

Understand how hPa and inHg relate. The converter is educational and does not replace approved aviation equipment, procedures, altimeter settings, or operational guidance.

Science and experiments

Convert measurements into pascals, kilopascals or atmospheres for physics examples and gas-law calculations.

Marine weather and navigation

Translate marine barometric pressure reports into familiar units while relying on current official forecasts for decisions at sea.

Engineering and instrument specifications

Compare pressure specifications in psi, kPa, Pa and atm. Always confirm whether an equipment specification refers to absolute or gauge pressure before converting or using the value.

DISCOVERY 08 / The pressure myth detector

Four things your barometer might surprise you with

01

hPa and mb are exactly equal.

A forecast of 1000 mb is exactly the same pressure as 1000 hPa. No rounding required.

02

High pressure doesn't guarantee sunshine.

Cloud cover and other weather conditions depend on more than a single pressure reading.

03

Two barometers may not show the same number.

Differences in altitude, calibration and whether pressure is reduced to sea level can all affect reported readings.

04

Pressure and pressure change are different things.

A pressure reading describes the current value. A rising or falling pressure trend describes how that value changes over time.

DISCOVERY 09 / Answers from the observatory

Atmospheric Pressure Converter FAQ

Practical answers to common questions about hPa, inHg, millibars, pascals, atmospheric pressure, and barometer readings.

What is an atmospheric pressure converter?
An atmospheric pressure converter translates pressure measurements between units such as hPa, mb, inHg, mmHg, Pa, kPa, atm and psi. It does not measure pressure; it converts the value you provide.
How do I convert hPa to inHg?
Divide the pressure in hectopascals by approximately 33.8638867. For example, 1013.25 hPa converts to approximately 29.9213 inHg.
How do I convert inHg to hPa?
Multiply the inches-of-mercury reading by approximately 33.8638867. For instance, 30 inHg is about 1015.92 hPa.
Is hPa the same as millibars?
Yes. One hectopascal equals exactly one millibar. A reading of 1020 hPa is therefore identical to 1020 mb.
What is normal atmospheric pressure at sea level?
The defined standard atmosphere is 1013.25 hPa, 1013.25 mb, 101.325 kPa, or approximately 29.92 inHg. Actual sea-level pressure varies with weather and should not be expected to remain at that reference value.
What does 29.92 inHg mean?
Approximately 29.92 inches of mercury corresponds to one defined standard atmosphere. In barometric weather reporting, inches of mercury is a traditional pressure measurement unit.
How many pascals are in one atmosphere?
One standard atmosphere equals exactly 101,325 pascals, or 101.325 kilopascals.
What is 1000 hPa in inches of mercury?
1000 hPa is approximately 29.53 inHg using the conventional pressure-unit relationship.
How do I convert hPa to mmHg?
Multiply hPa by approximately 0.7500616. This means 1000 hPa is approximately 750.06 mmHg.
How do I convert psi to kPa?
Multiply psi by approximately 6.894757. For example, 14.69595 psi is approximately 101.325 kPa.
Does low atmospheric pressure always mean rain?
No. Low-pressure systems are often associated with unsettled conditions, but rain depends on atmospheric moisture, movement, temperature and other factors. A single pressure reading cannot reliably predict rainfall.
Why does atmospheric pressure decrease with altitude?
Higher locations generally have less air above them. With less atmospheric weight overhead, pressure tends to be lower.
What is the difference between station pressure and sea-level pressure?
Station pressure is measured at the station's elevation. Sea-level pressure is adjusted to an equivalent sea-level reference to make pressure readings across different elevations easier to compare. A unit conversion alone does not perform this altitude adjustment.
Can this converter calculate pressure at another altitude?
No. This tool converts pressure units, not pressure changes caused by altitude. Altitude-based pressure calculations require additional assumptions or atmospheric measurements.
Can atmospheric pressure be zero or negative?
Zero absolute pressure represents a perfect vacuum. Ordinary absolute pressure is not negative. Gauge pressure can be negative relative to a reference pressure, but UtilityGlen's tool accepts absolute pressure values of zero or greater.
Does the tool show live local barometric pressure?
No. The calculator does not use location services, connect to a weather API or measure pressure. It converts your manually entered reading.
Is this Atmospheric Pressure Converter free?
Yes. The UtilityGlen Atmospheric Pressure Converter is free to use online without creating an account.
Does the converter work without an internet connection?
Its conversion calculations run locally in JavaScript. Once the page is loaded, those calculations don't require a weather API. Fully offline page loading depends on the availability of the page and its external assets.
Your barometer, decoded

Understand the pressure. Master the units.

Turn any barometric reading into eight familiar pressure units. Explore weather reference values, compare hPa with inHg, learn conversion formulas, and make sense of atmospheric pressure using UtilityGlen's free online converter.

Convert Pressure

Methodology, accuracy and scientific references

UtilityGlen performs unit conversions using standard pressure relationships expressed relative to the pascal. The calculator uses conventional mercury pressure units and standard definitions for atmosphere, millibar and psi. Displayed results may be rounded. The tool does not calculate pressure changes with elevation, distinguish automatically between station and sea-level pressure, or predict local weather.

For official definitions and atmospheric science explanations, explore:

NIST — Pressure Unit Conversions NOAA — Air Pressure Explained

For educational and general-purpose unit conversion. Consult calibrated measurements, official meteorological observations and relevant professional guidance when pressure data affects safety or operational decisions.

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