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Millibar to Inch of Mercury Converter

Convert millibars to inches of mercury with our free online pressure converter.

Quick Answer

1 Millibar = 0.02953 inches of mercury

Formula: Millibar × conversion factor = Inch of Mercury

Use the calculator below for instant, accurate conversions.

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All conversion formulas on UnitsConverter.io have been verified against NIST (National Institute of Standards and Technology) guidelines and international SI standards. Our calculations are accurate to 10 decimal places for standard conversions and use arbitrary precision arithmetic for astronomical units.

Last verified: February 2026Reviewed by: Sam Mathew, Software Engineer

Millibar to Inch of Mercury Calculator

How to Use the Millibar to Inch of Mercury Calculator:

  1. Enter the value you want to convert in the 'From' field (Millibar).
  2. The converted value in Inch of Mercury will appear automatically in the 'To' field.
  3. Use the dropdown menus to select different units within the Pressure category.
  4. Click the swap button (⇌) to reverse the conversion direction.
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How to Convert Millibar to Inch of Mercury: Step-by-Step Guide

Converting Millibar to Inch of Mercury involves multiplying the value by a specific conversion factor, as shown in the formula below.

Formula:

inHg = mbar × 0.02953

Example Calculation:

1 mbar = 0.02953 inHg

Disclaimer: For Reference Only

These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.

Not for professional use. Results should be verified before use in any critical application. View our Terms of Service for more information.

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What is a Millibar and a Inch of Mercury?

1 mbar = 100 Pa = 1 hPa (exactly) = 0.001 bar = 0.0145 PSI = 0.75 mmHg = 0.000987 atm

Key relationship: 1 mbar = 1 hPa (exact equivalence)

1 inHg = 3,386.39 Pa = 3.386 kPa = 33.86 mbar = 33.86 hPa = 0.491 PSI = 0.0334 bar = 0.0334 atm = 25.4 mmHg

Key relationship: 29.92 inHg = 1 atmosphere (exactly)

Origin: Mercury Column

The unit literally measures how high mercury rises:

  • Historical: Barometers invented in 1600s used mercury column
  • Measurement: Mercury rises/falls with atmospheric pressure
  • 1 inHg: Mercury column exactly 1 inch high
  • 29.92 inHg: Mercury rises 29.92 inches at sea level (1 atm)
  • Why mercury?: Highest density liquid (narrow barometer), visible, stable

Note: The Millibar is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Inch of Mercury belongs to the imperial/US customary system.

Common Uses and Applications: millibars vs inches of mercury

Explore the typical applications for both Millibar (imperial/US) and Inch of Mercury (imperial/US) to understand their common contexts.

Common Uses for millibars

Aviation: Altimeter settings (pilots say "1015 millibars"). Maritime: Marine weather forecasts, ship barometers. Meteorology: Historical weather data (pre-1980s). Diving: Depth pressure calculations (sometimes).

When to Use inches of mercury

US Weather: Barometric pressure in weather forecasts, NOAA reports - THE US standard. Aviation: Altimeter settings (US standard, some international - critical for flight safety). HVAC: Vacuum measurements, duct pressure, system diagnostics. Historical meteorology: Traditional US measurement since early 1900s.

Additional Unit Information

About Millibar (mbar)

Is mbar the same as hPa?

Yes! 1 mbar = 1 hPa exactly (just different names, same value)

Millibar (mbar):

  • Traditional meteorology unit (1900s-1980s)
  • Still used: Aviation, maritime, older weather services
  • Pilots/mariners: "Set altimeter to 1015 millibars"

Hectopascal (hPa):

  • SI-compliant name (1980s-present)
  • Modern: Weather services worldwide officially use hPa
  • Scientific: Consistent with SI unit system

No conversion needed: 1,013 mbar = 1,013 hPa (identical)

Why two names?: Transition to SI units in 1980s. Chose "hectopascal" because 1 hPa = 1 mbar exactly, making transition seamless. Old term persists in aviation/maritime.

How do I convert mbar to PSI?

Formula: PSI = mbar × 0.0145038

Examples:

  • 1,013 mbar = 14.7 PSI (sea level)
  • 1,000 mbar = 14.5 PSI
  • 900 mbar = 13.05 PSI (storm)
  • 800 mbar = 11.6 PSI
  • 500 mbar = 7.25 PSI (FL180)

mbar to PSI converter →

What is normal atmospheric pressure in mbar?

Standard sea level: 1,013.25 mbar (exactly, by definition)

Typical range: 980-1,050 mbar depending on weather

Pressure variations:

  • Fair weather (high): 1,020-1,040 mbar
  • Normal range: 1,000-1,020 mbar
  • Stormy (low): 980-1,000 mbar
  • Hurricane: <980 mbar

Regional/seasonal: Varies ±30 mbar from standard

Altitude: Decreases ~12 mbar per 100m near sea level

What mbar is considered high or low pressure?

High pressure (anticyclone):

  • Strong high: >1,030 mbar (stable, clear weather)
  • Moderate high: 1,020-1,030 mbar (fair weather)

Normal pressure: 1,005-1,020 mbar

Low pressure (cyclone):

  • Moderate low: 990-1,005 mbar (cloudy, possible rain)
  • Strong low: 970-990 mbar (rain, wind)
  • Very low: <970 mbar (storms, gales)

Extreme low: <920 mbar (major hurricanes/typhoons)

Context matters: 1,000 mbar may be "low" in winter high-pressure region, "high" in tropical area.

Why do pilots still say "millibar" instead of "hectopascal"?

Historical training: Aviation training used mbar for decades International: ICAO (aviation authority) still references millibars Brevity: "Millibar" rolls off tongue easier than "hectopascal" Tradition: Aviation conservative about terminology changes Communication: Older pilots, documents use mbar

Modern transition:

  • Official: ICAO now uses hPa in documents
  • Practice: Pilots use both terms interchangeably
  • Altimeter: Settings shown as "1013 hPa" or "1013 mb"

No confusion: Since 1 mbar = 1 hPa exactly, using either term causes no errors.

Maritime similar: Sailors also prefer "millibar" from tradition.

About Inch of Mercury (inHg)

How do I convert inHg to PSI?

Formula: PSI = inHg × 0.491154

Examples:

  • 29.92 inHg = 14.7 PSI (sea level)
  • 30 inHg = 14.74 PSI
  • 28 inHg = 13.75 PSI (hurricane)
  • 25 inHg = 12.28 PSI
  • 20 inHg = 9.82 PSI

inHg to PSI converter →

How many inHg is normal atmospheric pressure?

Standard sea level = 29.92 inHg (exactly 1 atmosphere)

Typical weather range: 29.4-30.5 inHg

Pressure variations:

  • High pressure: 30.2-30.5 inHg (fair weather)
  • Normal: 29.8-30.2 inHg
  • Low pressure: 29.4-29.8 inHg (rain likely)
  • Storm: <29.4 inHg

Barometer rising/falling:

  • Rising: Improving weather
  • Steady: Conditions stable
  • Falling: Weather deteriorating

How do I convert inHg to mbar or hPa?

Formula: mbar (or hPa) = inHg × 33.8639

Examples:

  • 29.92 inHg = 1,013.25 mbar = 1,013.25 hPa (standard)
  • 30.0 inHg = 1,016 mbar
  • 29.0 inHg = 982 mbar (low pressure)
  • 28.0 inHg = 948 mbar (hurricane)
  • 31.0 inHg = 1,050 mbar (high pressure)

inHg to mbar converter → inHg to hPa converter →

Why does US use inHg instead of mbar/hPa?

Historical: US adopted imperial/customary units Mercury barometers: Traditionally marked in inches in US Weather tradition: NOAA, Weather Channel use inHg since inception Familiarity: Public knows "normal is about 30 inches" Aviation: US pilots trained with inHg altimeter settings

Rest of world: Uses mbar or hPa (metric standard)

Conversion: 30 inHg ≈ 1,000 mbar (approximately)

Trend: Slow transition—some US reports now show both units

How do I read a mercury barometer in inHg?

How it works: Mercury column rises/falls with atmospheric pressure

Reading:

  • Look at top of mercury meniscus (curved surface)
  • Read scale at eye level to avoid parallax error
  • Scale typically 28-31 inHg range

Interpreting:

  • 30.2-30.5 inHg: High pressure (fair, clear weather)
  • 29.8-30.2 inHg: Normal (stable conditions)
  • 29.4-29.8 inHg: Low pressure (clouds, possible rain)
  • <29.4 inHg: Very low (storm likely)

Trend matters: Falling rapidly = weather worsening; Rising = improving

Adjustment: Correct for altitude (sea level reading)

Conversion Table: Millibar to Inch of Mercury

Millibar (mbar)Inch of Mercury (inHg)
0.50.015
10.03
1.50.044
20.059
50.148
100.295
250.738
501.477
1002.953
2507.383
50014.765
1,00029.53

People Also Ask

How do I convert Millibar to Inch of Mercury?

To convert Millibar to Inch of Mercury, enter the value in Millibar in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our pressure converter page to convert between other units in this category.

Learn more →

What is the conversion factor from Millibar to Inch of Mercury?

The conversion factor depends on the specific relationship between Millibar and Inch of Mercury. You can find the exact conversion formula and factor on this page. Our calculator handles all calculations automatically. See the conversion table above for common values.

Can I convert Inch of Mercury back to Millibar?

Yes! You can easily convert Inch of Mercury back to Millibar by using the swap button (⇌) in the calculator above, or by visiting our Inch of Mercury to Millibar converter page. You can also explore other pressure conversions on our category page.

Learn more →

What are common uses for Millibar and Inch of Mercury?

Millibar and Inch of Mercury are both standard units used in pressure measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our pressure converter for more conversion options.

For more pressure conversion questions, visit our FAQ page or explore our conversion guides.

Helpful Conversion Guides

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⚖️ Metric vs Imperial

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⚠️ Common Mistakes

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All Pressure Conversions

Pascal to KilopascalPascal to MegapascalPascal to HectopascalPascal to BarPascal to MillibarPascal to AtmospherePascal to Technical AtmospherePascal to TorrPascal to Millimeter of MercuryPascal to Inch of MercuryPascal to Pound per Square InchPascal to Kilopound per Square InchPascal to Kilogram-force per Square CentimeterPascal to Kilogram-force per Square MeterPascal to Millimeter of Water ColumnPascal to Inch of Water ColumnKilopascal to PascalKilopascal to MegapascalKilopascal to HectopascalKilopascal to BarKilopascal to MillibarKilopascal to AtmosphereKilopascal to Technical AtmosphereKilopascal to TorrKilopascal to Millimeter of MercuryKilopascal to Inch of MercuryKilopascal to Pound per Square InchKilopascal to Kilopound per Square InchKilopascal to Kilogram-force per Square CentimeterKilopascal to Kilogram-force per Square MeterKilopascal to Millimeter of Water ColumnKilopascal to Inch of Water ColumnMegapascal to PascalMegapascal to KilopascalMegapascal to HectopascalMegapascal to BarMegapascal to MillibarMegapascal to AtmosphereMegapascal to Technical AtmosphereMegapascal to TorrMegapascal to Millimeter of MercuryMegapascal to Inch of MercuryMegapascal to Pound per Square InchMegapascal to Kilopound per Square InchMegapascal to Kilogram-force per Square CentimeterMegapascal to Kilogram-force per Square MeterMegapascal to Millimeter of Water ColumnMegapascal to Inch of Water ColumnHectopascal to PascalHectopascal to KilopascalHectopascal to MegapascalHectopascal to BarHectopascal to MillibarHectopascal to AtmosphereHectopascal to Technical AtmosphereHectopascal to TorrHectopascal to Millimeter of MercuryHectopascal to Inch of MercuryHectopascal to Pound per Square InchHectopascal to Kilopound per Square InchHectopascal to Kilogram-force per Square CentimeterHectopascal to Kilogram-force per Square MeterHectopascal to Millimeter of Water ColumnHectopascal to Inch of Water ColumnBar to PascalBar to KilopascalBar to MegapascalBar to HectopascalBar to MillibarBar to AtmosphereBar to Technical AtmosphereBar to TorrBar to Millimeter of MercuryBar to Inch of MercuryBar to Pound per Square InchBar to Kilopound per Square InchBar to Kilogram-force per Square CentimeterBar to Kilogram-force per Square MeterBar to Millimeter of Water ColumnBar to Inch of Water ColumnMillibar to PascalMillibar to KilopascalMillibar to MegapascalMillibar to HectopascalMillibar to BarMillibar to AtmosphereMillibar to Technical AtmosphereMillibar to TorrMillibar to Millimeter of MercuryMillibar to Pound per Square InchMillibar to Kilopound per Square InchMillibar to Kilogram-force per Square CentimeterMillibar to Kilogram-force per Square MeterMillibar to Millimeter of Water ColumnMillibar to Inch of Water ColumnAtmosphere to PascalAtmosphere to KilopascalAtmosphere to MegapascalAtmosphere to HectopascalAtmosphere to BarAtmosphere to MillibarAtmosphere to Technical AtmosphereAtmosphere to TorrAtmosphere to Millimeter of MercuryAtmosphere to Inch of MercuryAtmosphere to Pound per Square InchAtmosphere to Kilopound per Square InchAtmosphere to Kilogram-force per Square CentimeterAtmosphere to Kilogram-force per Square MeterAtmosphere to Millimeter of Water ColumnAtmosphere to Inch of Water ColumnTechnical Atmosphere to PascalTechnical Atmosphere to KilopascalTechnical Atmosphere to MegapascalTechnical Atmosphere to HectopascalTechnical Atmosphere to BarTechnical Atmosphere to MillibarTechnical Atmosphere to AtmosphereTechnical Atmosphere to TorrTechnical Atmosphere to Millimeter of Mercury

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Verified Against Authority Standards

All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.

NIST Reference on Constants, Units and Uncertainty

National Institute of Standards and Technology — Fundamental physical constants and unit conversions

BIPM SI Units

Bureau International des Poids et Mesures — International System of Units (SI) definitions and standards

ISO 80000

International Organization for Standardization — Quantities and units international standards series

Last verified: February 19, 2026