Blood Pressure mmHg to kPa: Conversion Chart and Formula

The short answer

To convert a blood pressure reading from mmHg to kPa, multiply each number by 0.1333 (more precisely 0.133322). A reading of 120/80 mmHg is about 16.0/10.7 kPa. To go from kPa back to mmHg, multiply by 7.5. The Pressure Converter does this for you: choose mmHg (Torr) as the From unit, type the number and read kPa from the results.

Why there are two units

A blood pressure reading has two numbers: the systolic pressure (when the heart beats) over the diastolic pressure (between beats). Home monitors, clinic machines and most medical guidance express both in millimetres of mercury (mmHg), a unit that dates back to mercury-column instruments.

The kilopascal (kPa) is the SI unit of pressure. You may meet blood pressure in kPa in some textbooks, research papers, exam questions in physics or physiology, and occasionally in medical records from systems that use SI units throughout. The two units describe exactly the same pressure; only the scale differs.

The conversion factor

The US National Institute of Standards and Technology (NIST) lists the conventional millimetre of mercury as 133.3224 pascals. Since 1 kPa is 1,000 pascals:

• 1 mmHg = 0.1333224 kPa
• 1 kPa = 7.50062 mmHg

For everyday use, 0.1333 and 7.5 are accurate enough, because blood pressure readings are whole numbers and normally vary by several mmHg from one measurement to the next.

Formulas

• kPa = mmHg × 0.1333
• mmHg = kPa × 7.5

A quick mental shortcut: divide mmHg by 7.5. For 150 mmHg, 150 ÷ 7.5 = 20 kPa.

Blood pressure conversion chart (mmHg to kPa)

Values below come from the Pressure Converter, which uses 133.322 Pa per mmHg, rounded to one decimal place.

mmHg	kPa
60	8.0
70	9.3
80	10.7
90	12.0
100	13.3
110	14.7
120	16.0
130	17.3
140	18.7
150	20.0
160	21.3
180	24.0

Converting a full reading

Convert the two numbers separately and keep the same order.

Example 1: 120/80 mmHg

• Systolic: 120 × 0.133322 = 15.99864, which rounds to 16.0 kPa
• Diastolic: 80 × 0.133322 = 10.66576, which rounds to 10.7 kPa
• Reading: 16.0/10.7 kPa

Example 2: 135/85 mmHg

• 135 × 0.133322 = 17.998, about 18.0 kPa
• 85 × 0.133322 = 11.332, about 11.3 kPa
• Reading: 18.0/11.3 kPa

Example 3: a reading given as 16/10 kPa

• 16 × 7.50062 = 120.01, about 120 mmHg
• 10 × 7.50062 = 75.01, about 75 mmHg
• Reading: 120/75 mmHg

How to use the Pressure Converter

Open the Pressure Converter.

Type the systolic number in Value to convert.

In From, choose mmHg (Torr).

In the second dropdown, choose Kilopascal (kPa). The green box shows the result, and the table below lists the same pressure in Pa, MPa, bar, PSI, atm and inches of mercury.

Repeat for the diastolic number.

To convert kPa back to mmHg, press the swap button (⇄) between the boxes, or set From to kPa and the target to mmHg.

The results show up to eight decimal places, so round them yourself. One decimal place in kPa is normal; whole numbers are normal in mmHg.

Converting a log of readings in a spreadsheet

If you keep a diary of readings in Excel or Google Sheets, you do not need to convert each one by hand. Put systolic values in column A and diastolic values in column B, then:

• In C2, type =ROUND(A2*0.133322,1) for systolic in kPa
• In D2, type =ROUND(B2*0.133322,1) for diastolic in kPa
• Fill both formulas down the column

To convert a kPa log back to mmHg, use =ROUND(A2*7.50062,0) instead. Spot-check one row with the converter to make sure the columns are not swapped.

mmHg and Torr

The converter labels the unit mmHg (Torr). The torr is defined as exactly 1/760 of a standard atmosphere and is extremely close to the conventional mmHg (they differ by less than one part in a million). For blood pressure and almost every practical purpose you can treat them as the same unit.

Other units you might see

• cmH2O (centimetres of water) is used for some breathing equipment and venous pressure measurements. It is not in the converter list; 1 mmHg is about 1.36 cmH2O.
• psi and bar are used for tyres, gas cylinders and pumps, not blood pressure. For those, see Tyre Pressure PSI to Bar and kPa.
• atm (standard atmosphere) equals 760 mmHg or 101.325 kPa. Blood pressure readings are pressures above atmospheric pressure, which is why 120 mmHg is a small number compared with 760.

Common mistakes

• Converting only one number. Both systolic and diastolic need converting.
• Dividing instead of multiplying. mmHg to kPa makes the numbers smaller (multiply by 0.1333). If 120 mmHg became 900, the conversion went the wrong way.
• Mixing units in one reading. Do not write 16/80; keep both numbers in the same unit.
• Rounding too early. Convert, then round once at the end.

A note on interpreting readings

This page is about unit conversion only. Converting a reading does not change what it means, and categories such as normal or high blood pressure are defined in mmHg in most guidelines. If you are tracking your own blood pressure, keep a record in the unit your monitor and doctor use, and ask a doctor or pharmacist about what your readings mean for you.