Inch of Mercury (inHg) - Unit Information & Conversion
🔄 Quick Convert Inch of Mercury
What is a Inch of Mercury?
Inch of mercury (inHg) measures pressure by mercury column height in inches. US standard for barometric pressure, aviation altimeter settings. 1 inHg = 3,386.39 Pa ≈ 33.86 mbar. 29.92 inHg = 1 atmosphere. Used in US weather reports.
History of the Inch of Mercury
Imperial version of mmHg. Standard in US meteorology, aviation since early 1900s. Mercury barometer reads pressure as column height. Still used in US despite global SI adoption. NOAA weather reports use inHg.
Quick Answer
What is inHg? Inch of mercury (inHg) measures barometric pressure as mercury column height in inches. US standard for weather reports and aviation. 1 inHg = 3,386.39 Pa = 33.86 mbar. Normal sea level: 29.92 inHg. Use our pressure converter for conversions.
Definition
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)
Common Uses
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.
Real-World Examples
Weather System Pressures (inHg)
- Very high pressure: 30.5-31.0 inHg (clear, cold weather)
- High pressure system: 30.2-30.5 inHg (fair weather)
- Average sea level: 29.92 inHg (standard atmosphere)
- Normal range: 29.8-30.2 inHg
- Low pressure system: 29.4-29.8 inHg (cloudy, rain)
- Storm: 28.5-29.4 inHg (strong low pressure)
- Hurricane (Category 1): 28.5-29.0 inHg
- Hurricane (Category 3): 27.5-28.0 inHg
- Hurricane (Category 5): <27.2 inHg
- Strongest hurricane: 26.05 inHg (Typhoon Tip, 1979)
Altitude Pressure (inHg)
- Sea level: 29.92 inHg (standard)
- 1,000 ft (305m): 28.86 inHg
- 5,000 ft (1,524m): 24.89 inHg
- 10,000 ft (3,048m): 20.58 inHg (cabin pressure)
- Denver (5,280 ft): ~24.65 inHg
- Mount Everest summit: ~9.23 inHg
Aviation Altimeter Settings
- Standard: 29.92 inHg (ISA standard day)
- High pressure: 30.5-31.0 inHg
- Low pressure: 28.5-29.5 inHg
- Minimum (FAA): ~28.0 inHg (extreme low)
- Maximum (FAA): ~31.0 inHg (extreme high)
Geographic Variations
- San Francisco (sea level): ~29.92 inHg
- Denver (1,609m): ~24.65 inHg
- Death Valley (-86m): ~30.25 inHg (below sea level)
- Summit of Pikes Peak (4,302m): ~18.75 inHg
Inch of Mercury Conversion Formulas
To Pascal:
To Kilopascal:
To Megapascal:
To Hectopascal:
To Bar:
To Millibar:
To Atmosphere:
To Technical Atmosphere:
To Torr:
To Millimeter of Mercury:
To Pound per Square Inch:
To Kilopound per Square Inch:
To Kilogram-force per Square Centimeter:
To Kilogram-force per Square Meter:
To Millimeter of Water Column:
To Inch of Water Column:
Frequently Asked Questions
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 →
Convert Inch of Mercury
Need to convert Inch of Mercury to other pressure units? Use our conversion tool.
Inch of Mercury Quick Info
Related Pressure Units
Popular Conversions
- Inch of Mercury to PascalConvert →1 inHg = 3386.389 Pa
- Inch of Mercury to KilopascalConvert →1 inHg = 3.386389 kPa
- Inch of Mercury to MegapascalConvert →1 inHg = 0.003386 MPa
- Inch of Mercury to HectopascalConvert →1 inHg = 33.86389 hPa
- Inch of Mercury to BarConvert →1 inHg = 0.033864 bar
- Inch of Mercury to MillibarConvert →1 inHg = 33.86389 mbar