MMHG to INHG
Convert millimeters of mercury into inches of mercury for gauges, specs, hydraulic notes, and pressure reference checks.
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MMHG to INHG Table
| Millimeters of Mercury | Inches of Mercury |
|---|---|
| 1 | 0.0393700787 |
| 5 | 0.1968503937 |
| 10 | 0.3937007874 |
| 25 | 0.9842519685 |
| 50 | 1.968503937 |
| 100 | 3.937007874 |
| 250 | 9.842519685 |
| 500 | 19.68503937 |
| 1,000 | 39.37007874 |
| 2,500 | 98.42519685 |
Popular Conversions
- 1 millimeters of mercury = 0.0393700787 inches of mercury
- 5 millimeters of mercury = 0.1968503937 inches of mercury
- 10 millimeters of mercury = 0.3937007874 inches of mercury
- 25 millimeters of mercury = 0.9842519685 inches of mercury
- 50 millimeters of mercury = 1.968503937 inches of mercury
- 100 millimeters of mercury = 3.937007874 inches of mercury
- 250 millimeters of mercury = 9.842519685 inches of mercury
- 500 millimeters of mercury = 19.68503937 inches of mercury
What is Millimeters of Mercury and Inches of Mercury?
Millimeters of Mercury
Definition: Millimeters of mercury express pressure using the height of a mercury column.
History/origin: The unit comes from classic barometers and medical manometers that measured pressure as a fluid height.
Current use: MmHg is used in blood pressure, vacuum work, laboratory pressure readings, and older engineering references.
Inches of Mercury
Definition: Inches of mercury express pressure using a mercury column height in inches.
History/origin: The unit grew from barometers and aviation weather instruments that used mercury columns.
Current use: InHg is used in weather reports, altimeter settings, and vacuum references.
Related Pressure Conversions
Pressure values are commonly translated across SI, customary, and fluid-column units in the same job.
| Related Conversion | Factor or Rule | Formula |
|---|---|---|
| mmHg to kPa | × 0.133322387 | kPa = mmHg × 0.133322387 |
| MPa to psi | × 145.037738 | psi = MPa × 145.037738 |
| Pa to kPa | ÷ 1,000 | kPa = Pa ÷ 1,000 |
| Pa to psi | × 0.000145037738 | psi = Pa × 0.000145037738 |
| psi to bar | × 0.068947573 | bar = psi × 0.068947573 |
| psi to mmHg | × 51.714933 | mmHg = psi × 51.714933 |
| psia to psig | minus atmosphere | psig = psia – atmospheric pressure |
| psig to psia | plus atmosphere | psia = psig + atmospheric pressure |
Typical Use Cases
Frequently Asked Questions
Q: Why do pressure pages like MMHG to INHG change the number so much?
A: Pressure units are sized very differently, so the same physical pressure can need a much larger or much smaller number after conversion.
Q: What does 1 millimeters of mercury become in inches of mercury?
A: 1 millimeters of mercury equals 0.0393700787 inches of mercury, which is a helpful checkpoint for tire pressure, hydraulics, vacuum work, and process instrumentation.
Q: When should I keep the original pressure unit?
A: Keep it when the sensor, regulator, gauge, or specification you are reading already uses that unit. Convert only when the destination document or tool expects another scale.
Q: Why do some pressure answers become decimals while others become large integers?
A: That is simply the size difference between the unit systems involved. The physical pressure stays the same.
Q: How do I convert Inches of Mercury back into Millimeters of Mercury?
A: mmHg = inHg × 25.4. That reverse relationship is useful when the reading already starts in the target pressure unit.
Q: Is this exact or approximate?
A: The calculation uses an exact factor.