UnitsConverter

Inch of Mercury to Torr Converter

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

Quick Answer

1 Inch of Mercury = 25.400006 torr

Formula: Inch of Mercury × conversion factor = Torr

Use the calculator below for instant, accurate conversions.

Our Accuracy Guarantee

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: December 2025Reviewed by: Sam Mathew, Software Engineer

Inch of Mercury to Torr Calculator

How to Use the Inch of Mercury to Torr Calculator:

  1. Enter the value you want to convert in the 'From' field (Inch of Mercury).
  2. The converted value in Torr 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 Inch of Mercury to Torr: Step-by-Step Guide

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

Formula:

Torr = inHg × 25.4

Example Calculation:

1 inHg = 25.400006 Torr

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.

Need to convert to other pressure units?

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📋 Unit Symbols

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What is a Inch of Mercury and a Torr?

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)

1 Torr = 1/760 atm (exactly) = 133.322 Pa = 1.333 mbar ≈ 1 mmHg (0.000015% difference)

Key relationships:

  • 760 Torr = 1 atmosphere (exactly)
  • 1 Torr ≈ 1 mmHg (virtually identical)
  • 1 mTorr = 0.001 Torr (millitorr)

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

Common Uses and Applications: inches of mercury vs torr

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

Common Uses for inches of mercury

US Weather: Barometric pressure in weather forecasts, NOAA reports. Aviation: Altimeter settings (US standard, some international). HVAC: Vacuum measurements, duct pressure (sometimes). Historical: Traditional US measurement since mercury barometer invention.

When to Use torr

Vacuum Technology: High vacuum pumps, vacuum chambers, thin-film deposition. Physics Laboratories: Pressure measurement in evacuated systems. Chemistry: Vapor pressure measurements, distillation processes. Medicine: Blood pressure (often interchangeable with mmHg).

Additional Unit Information

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)

About Torr (Torr)

What is the difference between Torr and mmHg?

Almost identical: 1 Torr ≈ 1 mmHg (difference < 0.000015%)

Torr: Defined as exactly 1/760 atmosphere (by definition) mmHg: Based on mercury density at 0°C and standard gravity

Practical usage:

  • Vacuum technology: Prefers Torr (more precise definition)
  • Medicine: Prefers mmHg (traditional, familiar)
  • Chemistry: Uses both interchangeably

Conversion: For all practical purposes, treat them as equal.

Torr to mmHg converter →

How many torr in 1 atmosphere?

1 atm = 760 Torr (exactly, by definition)

Examples:

  • 2 atm = 1,520 Torr
  • 0.5 atm = 380 Torr
  • 0.001 atm = 0.76 Torr
  • 10⁻⁶ atm = 0.00076 Torr = 0.76 mTorr (millitorr)

Atmosphere to Torr converter →

How do I convert Torr to PSI?

Formula: PSI = Torr × 0.0193368

Examples:

  • 760 Torr = 14.7 PSI (1 atmosphere)
  • 120 Torr = 2.32 PSI (systolic blood pressure)
  • 80 Torr = 1.55 PSI (diastolic blood pressure)
  • 1 Torr = 0.0193 PSI
  • 0.001 Torr = 0.0000193 PSI

Torr to PSI converter →

How do I convert Torr to Pascals?

Formula: Pa = Torr × 133.322

Examples:

  • 1 Torr = 133.322 Pa = 0.133 kPa
  • 760 Torr = 101,325 Pa = 101.325 kPa (1 atm)
  • 0.001 Torr (1 mTorr) = 0.133 Pa
  • 10⁻⁶ Torr = 0.000133 Pa

Torr to Pascal converter →

Why use Torr instead of mmHg in vacuum technology?

Torr advantages:

  • Exact definition: 1/760 atm (no ambiguity)
  • Independent: Not dependent on mercury properties
  • Standard: Agreed upon by vacuum scientists
  • Precision: Better defined for scientific work

mmHg issues:

  • Temperature dependent: Mercury density varies
  • Gravity dependent: Varies slightly with location
  • Less precise: For ultra-high vacuum measurements

In practice: Both work fine for most applications, but Torr is preferred in vacuum physics and engineering.

Conversion Table: Inch of Mercury to Torr

Inch of Mercury (inHg)Torr (Torr)
0.512.7
125.4
1.538.1
250.8
5127
10254
25635
501,270
1002,540.001
2506,350.002
50012,700.003
1,00025,400.006

People Also Ask

How do I convert Inch of Mercury to Torr?

To convert Inch of Mercury to Torr, enter the value in Inch of Mercury 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.

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

The conversion factor depends on the specific relationship between Inch of Mercury and Torr. 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 Torr back to Inch of Mercury?

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

Learn more →

What are common uses for Inch of Mercury and Torr?

Inch of Mercury and Torr 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 Inch 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 Torr

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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: December 3, 2025