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Pressure

Convert inches of mercury to millimeters of mercury

1 inHg=25.4mmHg

Use the converter below to change any inches of mercury value into millimeters of mercury instantly — with formula, conversion table, and real-world examples.

25.4

Conversion formula

Forward
millimeters of mercury = inches of mercury × 25.4
Reverse
inches of mercury = millimeters of mercury × 0.03937

Example: 10 inHg × 25.4 = 254 mmHg.

About both units

From

Inch of Mercury

inHg

The inch of mercury equals about 3386 Pa. Used in US barometers, US aviation altimeter settings and some engineering. Standard sea-level pressure: 29.92 inHg.

Real-world: Sea-level standard: 29.92 inHg. Mountain pass at 3000 m: ~21 inHg. US aviation QNH given in inHg.
Read full inch of mercury reference →
To

Millimeter of Mercury

mmHg

The millimetre of mercury equals about 133.3 Pa — the pressure exerted by a 1 mm column of mercury at 0 °C under standard gravity. Traditionally and still used in medicine: blood pressure of 120/80 mmHg.

Real-world: Normal blood pressure: 120/80 mmHg. Atmospheric: 760 mmHg. Good vacuum: <1 mmHg.
Read full millimeter of mercury reference →

Inch of Mercury to Millimeter of Mercury conversion table

Common inches of mercury to millimeters of mercury values for quick reference.

Inch of Mercury (inHg)Millimeter of Mercury (mmHg)
1 inHg25.4 mmHg
5 inHg127 mmHg
10 inHg254 mmHg
25 inHg635 mmHg
50 inHg1,270 mmHg
100 inHg2,540 mmHg
200 inHg5,080 mmHg
500 inHg12,700 mmHg
1,000 inHg25,400 mmHg
5,000 inHg127,000.01 mmHg

Tips & common mistakes

Quick tips

  • 1 inHg ≈ 3386 Pa ≈ 33.86 mbar.
  • 29.92 inHg = 1013.25 mbar = 1 atm.
  • US pilots use inHg; European pilots use hPa (mbar).

Avoid these

  • Confusing inHg with mmHg — factor of 25.4.
  • Mixing US and European altimeter units on a single flight plan.
  • Using inHg on scientific papers — prefer Pa.

Frequently asked questions

How many millimeters of mercury in a inch of mercury?
One inch of mercury equals 25.4 millimeters of mercury.
How do I convert inches of mercury to millimeters of mercury?
Multiply the inch of mercury value by 25.4 to get the equivalent in millimeters of mercury.
What is 100 inches of mercury in millimeters of mercury?
100 inches of mercury equals 2,540 millimeters of mercury.
Is a inch of mercury bigger than a millimeter of mercury?
Yes. 1 inch of mercury equals 25.4 millimeters of mercury, so one inch of mercury is larger.
How to convert inches of mercury to millimeters of mercury without a calculator?
Multiply by 25.4 for a quick estimate; use a calculator for precise results.

Related pressure conversions

📊 See full comparison matrix →

More from Inch of Mercury

inHg → Pa
1 = 3,386.39 Pa
inHg → kPa
1 = 3.38639 kPa
inHg → MPa
1 = 0.003386 MPa
inHg → bar
1 = 0.03386 bar
inHg → mbar
1 = 33.8639 mbar
inHg → psi
1 = 0.4912 psi
inHg → atm
1 = 0.03342 atm
inHg → Torr
1 = 25.4 Torr

More to Millimeter of Mercury

Pa → mmHg
1 = 0.007501 mmHg
kPa → mmHg
1 = 7.50062 mmHg
MPa → mmHg
1 = 7,500.62 mmHg
bar → mmHg
1 = 750.062 mmHg
mbar → mmHg
1 = 0.7501 mmHg
psi → mmHg
1 = 51.7149 mmHg
atm → mmHg
1 = 760 mmHg
Torr → mmHg
1 = 1 mmHg

Conversions in other categories

WeightKilogram → PoundLengthKilometer → MileTemperatureCelsius → FahrenheitVolumeLiter → US GallonAreaSquare Meter → Square FootSpeedKilometer per Hour → Mile per HourEnergyKilojoule → KilocaloriePowerKilowatt → Mechanical Horsepower