Convert Millimetre of mercury to Inch of mercury
1 millimetre of mercury = 0.03937008 inch of mercury (inHg). For example, 10 millimetre of mercury = 0.3937008 inch of mercury and 100 millimetre of mercury = 3.937008 inch of mercury. Type any value below to convert millimetre of mercury to inch of mercury both ways โ it runs entirely in your browser.
Quick answer: Millimetre of mercury to Inch of mercury
1 Millimetre of mercury = 0.03937008 Inch of mercury (mmHg โ inHg). To convert millimetre of mercury to inch of mercury, multiply by 0.03937008. To convert inch of mercury to millimetre of mercury, multiply by 25.4. The converter at the top does this instantly and both ways; the sections below give the formula, worked examples, a full conversion chart and answers to the most common millimetre of mercury-to-inch of mercury questions.
How to convert Millimetre of mercury to Inch of mercury
To convert millimetre of mercury to inch of mercury, multiply the number of millimetre of mercury by the conversion factor 0.03937008, because 1 mmHg = 0.03937008 inHg. The conversion is linear, so the same factor works for any value โ whole numbers, decimals or fractions. For the reverse direction, 1 inHg = 25.4 mmHg, so you divide by 0.03937008 (or multiply by 25.4) to turn inch of mercury back into millimetre of mercury.
inHg = mmHg ร 0.03937008 ยท
mmHg = inHg ร 25.4
- Write down the value you want to convert, in millimetre of mercury.
- Multiply it by 0.03937008.
- The result is the same area/length/quantity expressed in inch of mercury.
Millimetre of mercury to Inch of mercury โ worked examples
Each row shows the exact arithmetic so you can follow the conversion step by step. For example, 5 millimetre of mercury is 0.1968504 inch of mercury because 5 mmHg ร 0.03937008 = 0.1968504 inHg.
| Millimetre of mercury | Calculation | Inch of mercury |
|---|---|---|
| 1 mmHg | 1 mmHg ร 0.03937008 = 0.03937008 inHg | 0.03937008 inHg |
| 2 mmHg | 2 mmHg ร 0.03937008 = 0.07874016 inHg | 0.07874016 inHg |
| 3 mmHg | 3 mmHg ร 0.03937008 = 0.1181102 inHg | 0.1181102 inHg |
| 5 mmHg | 5 mmHg ร 0.03937008 = 0.1968504 inHg | 0.1968504 inHg |
| 7 mmHg | 7 mmHg ร 0.03937008 = 0.2755906 inHg | 0.2755906 inHg |
| 10 mmHg | 10 mmHg ร 0.03937008 = 0.3937008 inHg | 0.3937008 inHg |
| 12 mmHg | 12 mmHg ร 0.03937008 = 0.4724409 inHg | 0.4724409 inHg |
| 15 mmHg | 15 mmHg ร 0.03937008 = 0.5905512 inHg | 0.5905512 inHg |
| 20 mmHg | 20 mmHg ร 0.03937008 = 0.7874016 inHg | 0.7874016 inHg |
| 25 mmHg | 25 mmHg ร 0.03937008 = 0.984252 inHg | 0.984252 inHg |
| 50 mmHg | 50 mmHg ร 0.03937008 = 1.968504 inHg | 1.968504 inHg |
| 100 mmHg | 100 mmHg ร 0.03937008 = 3.937008 inHg | 3.937008 inHg |
Common Millimetre of mercury to Inch of mercury conversions
These are the millimetre of mercury-to-inch of mercury values people look up most often. Every figure is computed from the exact factor, so you can rely on them for quick reference:
- 1 millimetre of mercury = 0.03937008 inch of mercury
- 2 millimetre of mercury = 0.07874016 inch of mercury
- 2.5 millimetre of mercury = 0.0984252 inch of mercury
- 3 millimetre of mercury = 0.1181102 inch of mercury
- 4 millimetre of mercury = 0.1574803 inch of mercury
- 5 millimetre of mercury = 0.1968504 inch of mercury
- 6 millimetre of mercury = 0.2362205 inch of mercury
- 7 millimetre of mercury = 0.2755906 inch of mercury
- 8 millimetre of mercury = 0.3149606 inch of mercury
- 9 millimetre of mercury = 0.3543307 inch of mercury
- 10 millimetre of mercury = 0.3937008 inch of mercury
- 12 millimetre of mercury = 0.4724409 inch of mercury
- 15 millimetre of mercury = 0.5905512 inch of mercury
- 20 millimetre of mercury = 0.7874016 inch of mercury
- 25 millimetre of mercury = 0.984252 inch of mercury
- 30 millimetre of mercury = 1.181102 inch of mercury
- 50 millimetre of mercury = 1.968504 inch of mercury
- 75 millimetre of mercury = 2.952756 inch of mercury
- 100 millimetre of mercury = 3.937008 inch of mercury
- 200 millimetre of mercury = 7.874016 inch of mercury
- 500 millimetre of mercury = 19.68504 inch of mercury
- 1000 millimetre of mercury = 39.37008 inch of mercury
Millimetre of mercury to Inch of mercury conversion chart (both directions)
The chart below converts millimetre of mercury to inch of mercury and inch of mercury to millimetre of mercury side by side, so it works whichever way you need. 1 millimetre of mercury = 0.03937008 inch of mercury, and 1 inch of mercury = 25.4 millimetre of mercury.
| Millimetre of mercury โ Inch of mercury | Inch of mercury โ Millimetre of mercury |
|---|---|
| 0.25 mmHg = 0.00984252 inHg | 0.25 inHg = 6.35 mmHg |
| 0.5 mmHg = 0.01968504 inHg | 0.5 inHg = 12.7 mmHg |
| 1 mmHg = 0.03937008 inHg | 1 inHg = 25.4 mmHg |
| 2 mmHg = 0.07874016 inHg | 2 inHg = 50.8 mmHg |
| 3 mmHg = 0.1181102 inHg | 3 inHg = 76.2 mmHg |
| 4 mmHg = 0.1574803 inHg | 4 inHg = 101.6 mmHg |
| 5 mmHg = 0.1968504 inHg | 5 inHg = 127 mmHg |
| 6 mmHg = 0.2362205 inHg | 6 inHg = 152.4 mmHg |
| 7 mmHg = 0.2755906 inHg | 7 inHg = 177.8 mmHg |
| 8 mmHg = 0.3149606 inHg | 8 inHg = 203.2 mmHg |
| 9 mmHg = 0.3543307 inHg | 9 inHg = 228.6 mmHg |
| 10 mmHg = 0.3937008 inHg | 10 inHg = 254 mmHg |
| 12 mmHg = 0.4724409 inHg | 12 inHg = 304.8 mmHg |
| 15 mmHg = 0.5905512 inHg | 15 inHg = 381 mmHg |
| 20 mmHg = 0.7874016 inHg | 20 inHg = 508 mmHg |
| 25 mmHg = 0.984252 inHg | 25 inHg = 635 mmHg |
| 30 mmHg = 1.181102 inHg | 30 inHg = 762 mmHg |
| 40 mmHg = 1.574803 inHg | 40 inHg = 1,016 mmHg |
| 50 mmHg = 1.968504 inHg | 50 inHg = 1,270 mmHg |
| 75 mmHg = 2.952756 inHg | 75 inHg = 1,905 mmHg |
| 100 mmHg = 3.937008 inHg | 100 inHg = 2,540 mmHg |
| 150 mmHg = 5.905512 inHg | 150 inHg = 3,810 mmHg |
| 200 mmHg = 7.874016 inHg | 200 inHg = 5,080 mmHg |
| 250 mmHg = 9.84252 inHg | 250 inHg = 6,350 mmHg |
| 500 mmHg = 19.68504 inHg | 500 inHg = 12,700 mmHg |
| 1000 mmHg = 39.37008 inHg | 1000 inHg = 25,400 mmHg |
Millimetre of mercury vs Inch of mercury: which is bigger?
A inch of mercury is the larger unit: one inch of mercury equals 25.4 millimetre of mercurys. Put another way, you need 25.4 millimetre of mercurys to make a single inch of mercury.
What is a Millimetre of mercury? History, origin and usage
Measuring pressure by the height of a mercury column dates to Torricelli in 1643 and became the standard laboratory method for three centuries. Mercury was chosen because it is dense enough to keep the tube a manageable length โ a water barometer measuring the same pressure would need to be over ten metres tall. The modern unit no longer depends on real mercury: it is fixed at exactly 133.322387415 pascals, the value a millimetre of mercury would give at a conventional density of 13,595.1 kg per cubic metre under standard gravity.
Millimetres of mercury are the universal unit of blood pressure โ a reading of "120 over 80" means 120 mmHg when the heart contracts and 80 mmHg between beats. They are also used for eye pressure, cerebrospinal fluid pressure and some vacuum work.
Mercury sphygmomanometers are being retired worldwide because of the toxicity of mercury, yet the unit has outlived the instrument: digital monitors with no mercury in them still report in mmHg, because a century of medical guidance is written in it.
What is a Inch of mercury? History, origin and usage
Inches of mercury come from the same barometers as millimetres of mercury, read off in imperial units. The unit stayed embedded in North American practice long after the metric system spread elsewhere, largely because aviation and broadcast weather standardised on it early and changing would have meant reissuing every altimeter and every chart.
Inches of mercury are used for atmospheric pressure in United States weather reports and, importantly, for altimeter settings in aviation in the US and Canada. They also appear on vacuum gauges for engines and air-conditioning work.
The standard sea-level pressure of 29.92 inHg is one of the most recognisable numbers in aviation โ pilots set it as the default altimeter reference. An inch of mercury is exactly 25.4 millimetres of mercury, because the inch itself has been exactly 25.4 mm since 1959.
Convert 1 Millimetre of mercury to other units
It can help to see a millimetre of mercury next to the other units it is commonly compared with. One millimetre of mercury (mmHg) is equal to:
| 1 Millimetre of mercury equals | Unit |
|---|---|
| 133.3224 Pa | Pascal |
| 1.333224 hPa | Hectopascal |
| 0.1333224 kPa | Kilopascal |
| 0.0001333224 MPa | Megapascal |
| 1.333224 mbar | Millibar |
| 0.001333224 bar | Bar |
| 0.00131579 atm | Standard atmosphere |
| 1 Torr | Torr |
| 0.03937008 inHg | Inch of mercury |
| 13.5951 mmHโO | Millimetre of water |
| 0.5352402 inHโO | Inch of water |
| 0.01933678 psi | Pound per square inch |
| 0.00135951 kgf/cmยฒ | Kilogram-force per square centimetre |
Convert 1 Inch of mercury to other units
One inch of mercury (inHg) is equal to:
| 1 Inch of mercury equals | Unit |
|---|---|
| 3,386.389 Pa | Pascal |
| 33.86389 hPa | Hectopascal |
| 3.386389 kPa | Kilopascal |
| 0.003386389 MPa | Megapascal |
| 33.86389 mbar | Millibar |
| 0.03386389 bar | Bar |
| 0.03342106 atm | Standard atmosphere |
| 25.4 Torr | Torr |
| 25.4 mmHg | Millimetre of mercury |
| 345.3155 mmHโO | Millimetre of water |
| 13.5951 inHโO | Inch of water |
| 0.4911541 psi | Pound per square inch |
| 0.03453155 kgf/cmยฒ | Kilogram-force per square centimetre |
Tips for converting Millimetre of mercury to Inch of mercury
- To go from millimetre of mercury to inch of mercury, multiply by 0.03937008; to go back, divide by 0.03937008 (or multiply by 25.4).
- For a quick mental estimate, remember that 1 millimetre of mercury โ 0.03937008 inch of mercury, so 10 millimetre of mercury โ 0.3937008 inch of mercury.
- The converter above keeps full precision; the tables round for readability, so use the tool for exact figures.
- Both fields update live as you type โ change either side to convert in that direction.
How to use this Millimetre of mercury to Inch of mercury converter
Type a number into the Millimetre of mercury field and the equivalent in Inch of mercury appears instantly โ there is no โconvertโ button to press and nothing is sent to a server, so it works offline once the page has loaded and is safe for any data. You can also type into the Inch of mercury field to convert the other way (inch of mercury to millimetre of mercury). Use the swap control to flip the two units, and copy the result with a single click. Because the calculation runs in your browser with full floating-point precision, the converter is more exact than the rounded figures shown in the reference chart above โ use the chart for quick look-ups and the tool for precise work.
Accuracy and method
Every figure on this page โ the formula, the worked examples, the conversion chart and the โconvert to other unitsโ tables โ is computed from a single verified conversion factor (1 mmHg = 0.03937008 inHg), never copied from a hand-typed lookup table that could drift. That factor is derived from each unitโs definition in terms of a common base unit, and an automated check re-verifies all of the siteโs factors on every update, so the numbers here stay correct over time. This matters for millimetre of mercury-to-inch of mercury conversions because a small rounding error in a published table compounds quickly at larger quantities; computing from the exact factor avoids that.
Sources
- NIST Special Publication 811 โ Guide for the Use of the SI โ publishes the exact metric equivalents of the customary pressure units. A psi is one pound of force over one square inch, and the 1959 international yard-and-pound agreement fixes the pound at exactly 0.453 592 37 kilogram and the inch at exactly 0.0254 metre, while standard gravity is fixed at exactly 9.806 65 m/sยฒ โ so psi, inches of mercury and inches of water are defined exactly rather than measured.
- BIPM โ The International System of Units (SI Brochure) โ the defining document for the SI, published by the International Bureau of Weights and Measures. It fixes the base unit that this conversion resolves to, which is why the factor here can be exact rather than approximate.
Pressure factors here come from fixed definitions, anchored to the pascal: a bar is exactly 100,000 Pa, one atmosphere is exactly 101,325 Pa, a torr is exactly a 760th of an atmosphere, and psi is built from the exact pound and the exact inch. Two of them โ psi and the torr โ work out to decimals that repeat forever, so where a number is shown rounded it is marked, not quietly trimmed.
Frequently asked questions
- How many inch of mercury are in 1 millimetre of mercury?
- 1 millimetre of mercury = 0.03937008 inch of mercury (inHg). To convert any number of millimetre of mercury to inch of mercury, multiply by 0.03937008.
- How do I convert millimetre of mercury to inch of mercury?
- Multiply the number of millimetre of mercury by 0.03937008. For example, 10 millimetre of mercury = 10 ร 0.03937008 = 0.3937008 inch of mercury, and 25 millimetre of mercury = 0.984252 inch of mercury.
- How many millimetre of mercury are in 1 inch of mercury?
- 1 inch of mercury = 25.4 millimetre of mercury. So to convert inch of mercury back to millimetre of mercury, multiply by 25.4.
- What is the formula to convert millimetre of mercury to inch of mercury?
- inch of mercury = millimetre of mercury ร 0.03937008. The reverse formula is millimetre of mercury = inch of mercury ร 25.4.
- How much is 100 millimetre of mercury in inch of mercury?
- 100 millimetre of mercury = 3.937008 inch of mercury. (And 1000 millimetre of mercury = 39.37008 inch of mercury.)
- Which is bigger, a millimetre of mercury or a inch of mercury?
- A inch of mercury is larger: 1 inch of mercury = 25.4 millimetre of mercury.
- Is this millimetre of mercury to inch of mercury converter accurate?
- Yes โ every value is computed from the exact 0.03937008 inHg per mmHg factor (not rounded look-up tables), and the factors are re-verified automatically on every update.
- Can I convert inch of mercury to millimetre of mercury too?
- Yes. The converter works both ways โ enter a value in either field. 1 inch of mercury = 25.4 millimetre of mercury.