Millimeters of mercury and kilopascals
The conventional millimeter of mercury is 133.322387415 pascals, the pressure of a 1 mm column of mercury under standard gravity. Blood pressure (120/80 mmHg) and vacuum gauges are read in mmHg.
A kilopascal is 1,000 pascals. Tire pressure in Canada and Australia, engineering specs and medical gas pressures use kPa.
Worked example
Convert 120 mmHg: 120 × 0.133322387415 = 15.99868649, so 120 millimeters of mercury is 15.99868649 kilopascals. Likewise 100 mmHg = 13.33223874 kPa.
Estimating in your head
Divide by 7.5 for a quick figure; it is off by about 0%. For 120 mmHg that gives 16 kPa, against 15.9987 exactly.
Going the other way
To convert kilopascals to millimeters of mercury, divide by 0.133322387415 (or multiply by 7.50061575846).
How this works
kPa = mmHg × 0.133322387415
1 mmHg = 133.322387415 Pa and 1 kPa = 1,000 Pa, both by definition, so the factor is their ratio: 0.133322387415 exactly. Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many kilopascals are in a millimeter of mercury?
1 millimeter of mercury = 0.133322387415 kilopascals, exactly. The value follows from the unit definitions, so it never changes.
How do I convert millimeters of mercury to kilopascals?
Multiply by 0.133322387415. For example, 100 mmHg × 0.133322387415 = 13.33223874 kPa.
What is 1,000 mmHg in kilopascals?
1,000 mmHg = 133.3223874 kPa. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically
- NIST SP 811 Appendix B.9 — Factors for units listed by kind of quantity
- Wikipedia — Pound per square inch
Reviewed Oct 17, 2026 · test vectors fixtures/units/pressure/mmhg-to-kpa/