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mmHg to PSI Converter

Convert mmHg to psi — and every other pressure unit — with this free mmHg to PSI converter. Switch between millimeters of mercury, pounds per square inch, kilopascals, bar, atmospheres, torr, and pascals in either direction, with exact conversion factors and a live gauge.

Common pressures

How it works

Pressure is force spread over an area, and every pressure unit is a different pairing of a force unit and an area unit. A millimeter of mercury (mmHg) comes from the old mercury barometer: it is the pressure that supports a column of mercury exactly one millimeter high. PSI means pounds per square inch — the force of one pound pushing on one square inch. The pascal, the metric unit, is one newton per square meter, and a kilopascal is 1,000 pascals. A bar is 100,000 pascals, and an atmosphere (atm) is the average air pressure at sea level. Different fields kept different units, so blood pressure is read in mmHg, tires in psi, and weather in hectopascals.

All of these units are tied together by exact definitions. Standard air pressure is defined as 101,325 pascals, which is also 760 mmHg and 14.6959 psi. That single fact gives the key factors: 1 mmHg equals 133.322 pascals, and 1 psi equals 6,894.76 pascals. Dividing one by the other, 1 psi equals 51.7149 mmHg, and 1 mmHg equals 0.0193368 psi. The torr is named after Torricelli, the inventor of the barometer, and is defined to be exactly the same as 1 mmHg, so converting between mmHg and torr changes nothing at all.

To convert mmHg to psi, multiply by 0.0193368 — or, equivalently, divide by 51.7149. To go the other way, multiply psi by 51.7149. For example, 760 × 0.0193368 = 14.6959 psi, and 32 psi × 51.7149 = 1,654.88 mmHg, which is the pressure in a car tire written the way a barometer would read it. For kilopascals, multiply mmHg by 0.133322, and for bar, multiply mmHg by 0.00133322. A quick mental shortcut is that 1 psi is about 52 mmHg, so 15 psi is roughly 780 mmHg — close enough for a rough check, but use the exact factor for anything medical or technical.

Blood pressure is where most people meet mmHg. A healthy reading of 120 over 80 means the pressure in the arteries peaks at 120 mmHg (about 2.32 psi) with each heartbeat and falls to 80 mmHg (about 1.55 psi) between beats. Those numbers look small in psi only because a square inch is a large area compared with the tiny cross-section of a blood vessel — the same pressure, different unit. Weather reports use the same scale in hectopascals, where 1,013 hPa is the same standard day as 760 mmHg. Whatever the unit, the converter above keeps the physics identical: it converts everything through pascals, the common base, so converting back and forth always returns the number you started with.

Worked example

A weather station reports standard sea-level pressure as 760 mmHg. What is that in psi, and what is it in kilopascals?

Step 1: Write down the pressure — 760 mmHg.
Step 2: Use the conversion factor — 1 mmHg = 0.0193368 psi.
Step 3: Multiply: 760 × 0.0193368 = 14.6959.
Step 4: Read the answer — 14.6959 psi, usually rounded to 14.70 psi.
Step 5: For kilopascals, multiply by 0.133322: 760 × 0.133322 = 101.325 kPa.

Enter 760 in the converter with mmHg to psi selected and it gives exactly the same result: 14.6959 psi, with 101.325 kPa shown in the full table below. Going the other way, 1 atm converts to 101.325 kPa, 760 mmHg, and 14.6959 psi — all the same pressure in different units.

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