Mm to Atm

Barometric Metrology & ISO 80000-4 Pressure Standards

The standard atmosphere is legally defined based on the height of a mercury column in a Torricellian barometer (1 Standard Atmosphere 760 mmHg Exact):

• 1 Standard Atmosphere (atm): 760 mmHg = 760 Torr = 101,325 Pa = 101.325 kPa = 1.01325 bar = 14.696 psi = 29.921 inHg

Primary Pressure Scale Benchmarks

• 80 mmHg (Diastolic BP): = 0.1053 atm = 10.67 kPa

• 120 mmHg (Systolic BP): = 0.1579 atm = 16.00 kPa

• 740 mmHg (Storm Low): = 0.9737 atm = 98.66 kPa

• 760 mmHg (Standard Sea Level): 1.0000 atm = 101.33 kPa

• 780 mmHg (Anticyclone High): = 1.0263 atm = 103.99 kPa

• 1,520 mmHg (2.0 atm): = 2.0000 atm = 202.65 kPa

• 7,600 mmHg (10.0 atm): = 10.0000 atm = 1,013.25 kPa

Equations

• Atmospheres (atm) = mmHg760

• mmHg (Torr) = Atmospheres (atm) × 760

How to Use This Calculator

Enter your Pressure Value to Convert (e.g. 760.0), Barometric & Clinical Pressure Preset — choose from Custom Pressure Value, 760 mmHg (1.000 atm / Standard Sea-Level Pressure), 740 mmHg (0.974 atm / Low Pressure Storm Center), and Conversion Direction — choose from Millimeters of Mercury to Atmospheres (mmHg → atm / divide by 760), Atmospheres to Millimeters of Mercury (atm → mmHg / multiply by 760). Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Conversion factors used in this calculator:

1 atm = 760 mmHg exact

Worked Example

A laboratory barometer reading 760 mmHg at sea level indicates exactly 1.0000 standard atmosphere (101.325 kPa or 29.92 inHg).

Understanding Your Result

Unit conversion precision: round to the same number of significant figures as your original measurement. Converting 6 feet to meters gives 1.8288 m — but if your measurement was approximate (±1 inch), expressing more than 2 decimal places is false precision. For international trade and technical specifications, SI units (meters, kilograms, liters) are the standard. US customary units (feet, pounds, gallons) differ from Imperial UK units: 1 US gallon = 3.785 L vs. 1 UK gallon = 4.546 L.