mmHg to PSI Converter
Both ends of this conversion are defined rather than measured. The conventional millimetre of mercury is exactly 133.322387415 pascals, a millimetre of mercury at a density of 13,595.1 kg/m³ under a standard gravity of 9.80665 m/s², and one pound per square inch is a pound force of 4.4482216152605 N spread over 0.00064516 m², which is 6,894.757293168 pascals to the thirteen digits this table carries. So psi = mmHg × 133.322387415 / 6,894.757293168, which is a division by 51.7149252039. That makes 1 mmHg 0.0193367774595 psi, 50 mmHg 0.966838872973 psi, 100 mmHg 1.93367774595 psi, 300 mmHg 5.80103323784 psi, 750 mmHg 14.5025830946 psi and 760 mmHg 14.6959508692 psi. This page opens the converter with mmHg in the From box and Pound per square inch (psi) in the To box, ahead of whatever pair you converted last, and the list under the answer carries the same pressure in pascals, kilopascals, bar and atmospheres, so 760 mmHg reads 101,325.014435 Pa, 101.325014435 kPa, 1.01325014435 bar and 1.00000014247 atm beside its 14.6959508692 psi. The unit turns up on vacuum gauges, barometers and clinical monitors, and converting it changes the units on a number without changing what that number describes.
1 mmHg in every pressure unit
Common questions
- How many psi is 1 mmHg?
- 0.0193367774595 psi, which is 133.322387415 / 6,894.757293168. It scales straight up: 10 mmHg is 0.193367774595 psi, 50 mmHg is 0.966838872973 psi, 100 mmHg is 1.93367774595 psi, 500 mmHg is 9.66838872973 psi and 1,000 mmHg is 19.3367774595 psi. Answers print to twelve significant digits, so a small figure stays readable: 0.001 mmHg is 0.0000193367774595 psi.
- What is the formula for mmHg to psi?
- Pounds per square inch = millimetres of mercury × 133.322387415 / 6,894.757293168, or the same thing as a division by 51.7149252039. The other direction is millimetres of mercury = psi × 51.7149252039, so 1 psi is 51.7149252039 mmHg. The swap button between the two boxes reverses the pair, which turns this into a psi to mmHg converter without a reload.
- Is 760 mmHg the same as 14.7 psi?
- Close, and this page shows the difference. 760 mmHg converts to 14.6959508692 psi, while one standard atmosphere, which is exactly 101,325 Pa, is 14.6959487755 psi. The 14.7 you see quoted is that atmosphere rounded to three figures. The tiny gap between the two is not rounding, though: it is the difference between a torr and a conventional millimetre of mercury, which shows up at the eighth digit.
- Why is a torr not exactly a millimetre of mercury?
- Because the torr is defined as one seven hundred and sixtieth of a standard atmosphere, exactly 101,325 / 760 = 133.322368421 Pa, while the conventional mmHg is fixed at 133.322387415 Pa by the mercury density and gravity written into it. The mmHg is larger by about fourteen parts in a hundred million, which is why this page reads 760 mmHg as 1.00000014247 atm rather than exactly 1. For anything short of metrology, one torr and one mmHg are the same number.
- Does it matter whether my figure is gauge or absolute pressure?
- It matters for what the figure means, and the converter cannot tell the two apart: it changes units and never adds or removes an atmosphere on your behalf. A reading of 300 mmHg taken as absolute is 5.80103323784 psi. The same 300 mmHg quoted as a rise above a 760 mmHg ambient describes 1,060 mmHg absolute, which is 20.496984107 psi. Settle which convention your number uses before you convert it, because nothing in the arithmetic will flag a mix-up.
- Can I convert inches of mercury or vacuum microns here?
- Not as listed units, but both are millimetres of mercury in disguise. An inch is exactly 25.4 mm, so 1 inHg is 25.4 mmHg, which this page reads as 0.49115414747 psi. A vacuum micron is a thousandth of a torr, near enough a thousandth of a mmHg, so type 0.001 and the answer is 0.0000193367774595 psi. The pressure category itself holds pascals, kilopascals, bar, pounds per square inch, atmospheres and millimetres of mercury.
- Why does the list under the answer not repeat mmHg?
- The list shows every other unit in the category and skips the one you are converting from, so here it reads pascals, kilopascals, bar, pounds per square inch and atmospheres. The readout strip also carries an Uncommon units switch labelled Show 1 more, because mmHg is filed as the one uncommon pressure unit. On this page turning it on changes nothing you can see: the unit it would add is the one already sitting in the From box.
- Why does the page open on mmHg and psi when I last converted something else?
- Because a page that names a pair should show that pair. This one sets millimetres of mercury and pounds per square inch on arrival, ahead of whatever the converter last remembered, and it leaves the main unit converter's own pair alone: go back there and it is still on the units you left it on. The number you last typed does travel with you, along with the uncommon units switch, since that is usually the figure you are still working on.
Conversion factors are the exact legal definitions where one exists. An inch is exactly 2.54 cm and a pound exactly 0.45359237 kg, so those conversions are exact rather than approximate. Temperature uses offsets rather than factors, and that is shown in the working.