Convert millimeters of mercury or millimeters of water to psi and reverse psi to either pressure-head unit, with Pa, kPa, inHg, and inH2O results.

Convert a pressure-head unit to pounds-force per square inch.

Uses conventional mercury or water head units. Signed values can represent gauge pressure or pressure differences. This does not change gauge pressure to absolute pressure.

mm To psi Formula

The following formula is used to convert millimeters of mercury (mmHg) to pounds per square inch (psi).

PSI ≈ MMHG × 0.0193367775

Variables:

  • PSI is the pressure in pounds per square inch
  • MMHG is the pressure in millimeters of mercury

To calculate the pressure in pounds per square inch, multiply the pressure in conventional millimeters of mercury by approximately 0.0193367775. For conventional water head, use approximately 0.0014223343 psi per mmH₂O.

Pascals (Pa) to Kilopascals (kPa) Conversion Table
Pascals (Pa) Kilopascals (kPa)
1000.100
2500.250
5000.500
7500.750
10001.000
20002.000
25002.500
50005.000
75007.500
1000010.000
2500025.000
5000050.000
7500075.000
100000100.000
101325101.325
200000200.000
250000250.000
500000500.000
750000750.000
10000001000.000
* Rounded to 3 decimals. SI relation: 1 kPa = 1000 Pa (so 1 Pa = 0.001 kPa).

What Does “mm to psi” Mean?

Here, mm means a pressure-head unit, either millimeters of mercury (mmHg) or millimeters of water (mmH₂O), selected in the calculator. Linear millimeters alone cannot convert to psi. Both are units of pressure commonly used in various fields. Millimeters of mercury is often used in medicine and physiology, while pounds per square inch is widely used in the engineering and technical fields. The conversion is necessary when one needs to express measurements in different units for specific applications.

How to Calculate mm To psi?

The following steps outline how to calculate the pressure in pounds per square inch (PSI) from millimeters of mercury (mmHg) using the conventional mercury formula PSI ≈ MMHG * 0.0193367775. Choose the pressure medium and conversion direction before entering a value; the reference remains gauge, absolute, or differential as supplied.

  1. First, determine the pressure in millimeters of mercury (MMHG).
  2. Next, multiply conventional mmHg by approximately 0.0193367775. Water head uses a different factor: 1 conventional mmH₂O = 9.80665 Pa.
  3. Finally, calculate the pressure in pounds per square inch (PSI).
  4. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Pressure in conventional millimeters of mercury (mmHg) = 50. The equivalent is approximately 0.96683887 psi. Conventional water and mercury units use standard gravity; temperature-specific real column densities can differ.