Convert Millimeters of Mercury to Inches of Mercury
Instantly convert Millimeters of Mercury (mmHg) to Inches of Mercury (inHg) with our free online calculator.
Formula: mmHg to inHg — multiply by 0.0393699
Reference Table
| Millimeters of Mercury (mmHg) | Inches of Mercury (inHg) |
|---|---|
| 1 | 0.0393699 |
| 5 | 0.19685 |
| 10 | 0.393699 |
| 25 | 0.984249 |
| 50 | 1.9685 |
| 100 | 3.93699 |
How to Convert Millimeters of Mercury to Inches of Mercury
Formula
To convert Millimeters of Mercury (mmHg) to Inches of Mercury (inHg): multiply by 0.0393699
Step-by-Step
- Start with your value in Millimeters of Mercury (mmHg).
- Multiply by 0.0393699 to perform the conversion.
- The result is your value expressed in Inches of Mercury (inHg).
Conversion Factor
1 mmHg = 0.0393699 inHg
Reverse Factor
1 inHg = 25.4001 mmHg
Worked Example
Convert 25 Millimeters of Mercury to Inches of Mercury: 25 mmHg = 0.984249 inHg
About Millimeters of Mercury (mmHg)
A unit of pressure historically defined as the pressure exerted by a column of mercury exactly 1 millimeter tall at the standard acceleration of gravity (9.80665 m/s²) and the standard density of mercury (13,595.1 kg/m³ at 0 °C). The mmHg's contemporary definition rounds to exactly 133.322387415 Pa (NIST SP 811). Despite being non-SI, mmHg remains the international clinical standard for blood pressure measurement ("120 over 80" mmHg) per WHO and ESH guidelines, and is the default unit for intraocular pressure in ophthalmology (normal IOP 10-21 mmHg per Glaucoma Research Foundation) and intracranial pressure monitoring in neurology. Numerically the mmHg is almost identical to the torr (1 mmHg ≈ 1.0000007 torr — the difference is whether one uses the conventional density or the experimentally measured density of mercury). Barometric atmospheric pressure was historically quoted in mmHg before kPa/hPa adoption (760 mmHg = 1 atm = 101.325 kPa).
About Inch of Mercury (inHg)
A pressure unit defined as the pressure exerted by a 1-inch column of mercury at the standard density of mercury (0 °C) and the standard acceleration of gravity (≈ 3,386.389 Pa per NIST SP 811). Inches of mercury are the primary unit in US aviation for altimeter settings (the QNH datum is reported in inHg in METAR weather observations — "Altimeter 30.12 inHg" means 30.12 inHg corrected to mean sea level), US barometric weather reporting on consumer indoor weather stations and TV weather graphics, HVAC and refrigeration duct/return static pressure (often quoted as fractions of an inHg, e.g., 0.25 inHg = ~62 Pa), and some legacy automotive vacuum gauges measuring intake-manifold vacuum below atmospheric (a healthy engine reads ~18-22 inHg of vacuum at idle). Standard sea-level atmospheric pressure is 29.92 inHg = 1013.25 hPa = 101.325 kPa.
Quick Facts
- 1 Millimeters of Mercury equals 0.0393699 Inches of Mercury
- 1 Inch of Mercury equals 25.4001 Millimeters of Mercury
- Millimeters of Mercury is a unit of pressure
- Inch of Mercury is a unit of pressure
- This conversion is commonly used in tire inflation, weather reporting, scuba diving, and engineering
- The Millimeters of Mercury belongs to the metric system
- The Inch of Mercury belongs to the imperial system
Common Millimeters of Mercury to Inch of Mercury Conversions
| Millimeters of Mercury (mmHg) | Inches of Mercury (inHg) |
|---|---|
| 0.1 | 0.00393699 |
| 0.5 | 0.019685 |
| 1 | 0.0393699 |
| 2 | 0.0787399 |
| 5 | 0.19685 |
| 10 | 0.393699 |
| 14.696 | 0.578581 |
| 15 | 0.590549 |
| 20 | 0.787399 |
| 25 | 0.984249 |
| 50 | 1.9685 |
| 100 | 3.93699 |
| 150 | 5.90549 |
| 200 | 7.87399 |
| 500 | 19.685 |
| 1000 | 39.3699 |
Understanding Millimeters of Mercury
The Millimeters of Mercury (symbol: mmHg) is a unit of pressure. A unit of pressure historically defined as the pressure exerted by a column of mercury exactly 1 millimeter tall at the standard acceleration of gravity (9.80665 m/s²) and the standard density of mercury (13,595.1 kg/m³ at 0 °C). The mmHg's contemporary definition rounds to exactly 133.322387415 Pa (NIST SP 811). Despite being non-SI, mmHg remains the international clinical standard for blood pressure measurement ("120 over 80" mmHg) per WHO and ESH guidelines, and is the default unit for intraocular pressure in ophthalmology (normal IOP 10-21 mmHg per Glaucoma Research Foundation) and intracranial pressure monitoring in neurology. Numerically the mmHg is almost identical to the torr (1 mmHg ≈ 1.0000007 torr — the difference is whether one uses the conventional density or the experimentally measured density of mercury). Barometric atmospheric pressure was historically quoted in mmHg before kPa/hPa adoption (760 mmHg = 1 atm = 101.325 kPa).
It belongs to the metric measurement system.
Millimeters of Mercury are commonly used in tire inflation, weather reporting, scuba diving, and engineering.
Understanding Inches of Mercury
The Inch of Mercury (symbol: inHg) is a unit of pressure. A pressure unit defined as the pressure exerted by a 1-inch column of mercury at the standard density of mercury (0 °C) and the standard acceleration of gravity (≈ 3,386.389 Pa per NIST SP 811). Inches of mercury are the primary unit in US aviation for altimeter settings (the QNH datum is reported in inHg in METAR weather observations — "Altimeter 30.12 inHg" means 30.12 inHg corrected to mean sea level), US barometric weather reporting on consumer indoor weather stations and TV weather graphics, HVAC and refrigeration duct/return static pressure (often quoted as fractions of an inHg, e.g., 0.25 inHg = ~62 Pa), and some legacy automotive vacuum gauges measuring intake-manifold vacuum below atmospheric (a healthy engine reads ~18-22 inHg of vacuum at idle). Standard sea-level atmospheric pressure is 29.92 inHg = 1013.25 hPa = 101.325 kPa.
It belongs to the imperial measurement system.
Inches of Mercury are commonly used in tire inflation, weather reporting, scuba diving, and engineering.
Why Convert Millimeters of Mercury to Inches of Mercury?
Engineers, mechanics, and scientists frequently need to convert pressure between Millimeters of Mercury and Inches of Mercury when working with different measurement standards. Tire pressure, blood pressure readings, weather barometric measurements, and industrial process specifications may all use different pressure units depending on the region or discipline. Reliable conversion prevents equipment misuse and ensures safety.
Frequently Asked Questions
How do I convert Millimeters of Mercury to Inches of Mercury?
A unit of pressure historically defined as the pressure exerted by a column of mercury exactly 1 millimeter tall at the standard acceleration of gravity (9. To convert Millimeters of Mercury to Inches of Mercury, multiply by 0.0393699. For example, 25 mmHg equals 0.984249 inHg.
How many Inches of Mercury are in 1 Millimeters of Mercury?
There are 0.0393699 Inches of Mercury in 1 Millimeters of Mercury.
How many Millimeters of Mercury are in 1 Inch of Mercury?
There are 25.4001 Millimeters of Mercury in 1 Inch of Mercury.
What is the formula for Millimeters of Mercury to Inch of Mercury conversion?
The formula is: multiply by 0.0393699. This means 1 mmHg = 0.0393699 inHg.
Is a Millimeters of Mercury bigger than a Inch of Mercury?
Yes. One Millimeters of Mercury is larger than one Inch of Mercury because 1 mmHg equals 0.0393699 inHg, which is less than 1.
When do you need to convert between Millimeters of Mercury and Inches of Mercury?
A pressure unit defined as the pressure exerted by a 1-inch column of mercury at the standard density of mercury (0 °C) and the standard acceleration of gravity (≈ 3,386. Millimeters of Mercury and Inch of Mercury are both pressure units, so conversion comes up whenever one source of information uses one unit and another uses the other — a classic cross-reference challenge in engineering, trade, travel, and everyday life.