This page converts millitorr into inches of mercury using the factor 3.937006895e-05, and shows the reverse figure alongside it. Both units measure pressure, which is why one number does the whole job.
One thousandth of a torr, the working unit of vacuum deposition. US aviation and weather altimeter setting unit.
Gauge versus absolute. A tyre gauge reading 32 psi means 32 psi above atmospheric, which is about 46.7 psi absolute. Converting the number is straightforward; remembering which zero it was measured from is where the mistakes happen. N/mm² and MPa are the same size, so a drawing quoting either is quoting the same stress. Below the calculator there is a step table for the values people look up most, and a second table putting real pressure figures into inches of mercury so the number you get has something to be compared against.
The formula
millitorr- The amount you are converting, in millitorr
3.93700689499e-05- The exact number of inches of mercury in one millitorr
inches of mercury- The converted result
How it works, step by step
- Enter the value in millitorr.
- It is multiplied by 3.93700689499e-05, the exact factor between the two units.
- The answer is shown in inches of mercury, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A steam boiler: 7.5e+06 mTorr in inches of mercury
Take a steam boiler, roughly 7.5e+06 mTorr. The conversion is a single multiplication — 7.5e+06 × 3.93701e-05 — giving 295.276 inHg. Because the relationship is proportional, doubling the input doubles the answer to 590.551 inHg.
A domestic water main: 3e+06 mTorr in inches of mercury
Take a domestic water main, roughly 3e+06 mTorr. The conversion is a single multiplication — 3e+06 × 3.93701e-05 — giving 118.11 inHg. Because the relationship is proportional, doubling the input doubles the answer to 236.22 inHg.
How to read your score
Frequently asked questions
How many inches of mercury are in one millitorr?
Exactly 3.93700689499e-05. Every figure on this page is that one number multiplied by your input, so the only rounding is at the display step.
What is the formula to convert millitorr to inches of mercury?
inches of mercury = millitorr × 3.93700689499e-05. Reversed, millitorr = inches of mercury ÷ 3.93700689499e-05, which is the same as multiplying by 25,400.0063163.
Which is the bigger unit, the millitorr or the inch of mercury?
The inch of mercury. One millitorr is only 3.93701e-05 of a inch of mercury, so it takes 25,400 millitorr to make one inch of mercury.
What does this quantity actually measure?
Both units measure pressure. That is why a single factor is enough: there is no temperature offset and no material property involved, unlike conversions that cross between different quantities.
What is a millitorr?
One thousandth of a torr, the working unit of vacuum deposition.
What is a inch of mercury?
US aviation and weather altimeter setting unit.
Why does my answer differ from another converter?
Almost always because the other tool rounded the factor before multiplying. This page keeps full double precision through the calculation and rounds only for display, and it prints the factor it used so you can see where any difference came from.
Is there a quick way to do mTorr to inHg in my head?
Plenty of people do this in their head: divide by 25,000 instead of using the exact factor 0.000039. At 100 that shortcut gives 0.004 inches of mercury, off by 0.000063 inches of mercury or about 1.60%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Millitorr to inches of mercury reference tables
| Millitorr | Inches Of Mercury |
|---|---|
| 0.5 mTorr | 1.9685e-05 inHg |
| 1 mTorr | 3.93701e-05 inHg |
| 2 mTorr | 7.87401e-05 inHg |
| 3 mTorr | 0.00011811 inHg |
| 5 mTorr | 0.00019685 inHg |
| 10 mTorr | 0.000393701 inHg |
| 20 mTorr | 0.000787401 inHg |
| 25 mTorr | 0.000984252 inHg |
| 50 mTorr | 0.0019685 inHg |
| 75 mTorr | 0.00295276 inHg |
| 100 mTorr | 0.00393701 inHg |
| 250 mTorr | 0.00984252 inHg |
| 500 mTorr | 0.019685 inHg |
| 1000 mTorr | 0.0393701 inHg |
| 5000 mTorr | 0.19685 inHg |
Exact factor: 1 millitorr = 3.93700689499e-05 inches of mercury.
| Quantity | mTorr | inHg |
|---|---|---|
| Sea-level air | 7.6e+05 mTorr | 29.92 inHg |
| A car tyre | 1.655e+06 mTorr | 65.15 inHg |
| Blood pressure, systolic | 1.2e+05 mTorr | 4.724 inHg |
| A bicycle tyre | 4.654e+06 mTorr | 183.2 inHg |
| A domestic water main | 3e+06 mTorr | 118.1 inHg |
| A steam boiler | 7.501e+06 mTorr | 295.3 inHg |
Published reference values, converted with the same factor this page uses.