Pressure Converter
Solve pressure problems step-by-step with our free calculator. See formulas, worked examples, and clear explanations.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator
Pressure Converter
Calculator
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Formula: target = input * (input_toPa / target_toPa)
Worked example — 1 atm = 101325 Pa = 1.013 bar = 14.696 psi = 760 Torr
Formula
target = input * (input_toPa / target_toPa)
Pressure conversion works by converting the input value to pascals using the known conversion factor, then dividing by the target unit factor. For example, 1 atm = 101325 Pa, and 1 psi = 6894.757 Pa, so 1 atm = 101325/6894.757 = 14.696 psi.
Worked Examples
Example 1: Converting 1 Atmosphere to All Units
Problem:Convert standard atmospheric pressure (1 atm) to pascals, bar, PSI, Torr, and mmHg.
Solution:1 atm = 101,325 Pa 1 atm = 1.01325 bar 1 atm = 14.6960 psi 1 atm = 760.0000 Torr 1 atm = 760.0000 mmHg 1 atm = 29.9213 inHg 1 atm = 1013.25 mbar
Result:1 atm = 101325 Pa = 1.013 bar = 14.696 psi = 760 Torr
Example 2: Tire Pressure Conversion
Problem:A tire is inflated to 32 PSI. Convert to bar, kPa, and atmospheres.
Solution:32 PSI to Pa: 32 * 6894.757 = 220,632.2 Pa To kPa: 220,632.2 / 1000 = 220.632 kPa To bar: 220,632.2 / 100,000 = 2.2063 bar To atm: 220,632.2 / 101,325 = 2.1776 atm
Result:32 PSI = 2.2063 bar = 220.632 kPa = 2.1776 atm
Frequently Asked Questions
What is pressure and how is it measured?
Pressure is defined as force per unit area, measured in pascals (Pa) in the SI system, where one pascal equals one newton per square meter. Pressure exists in many forms: atmospheric pressure from the weight of air above us, hydraulic pressure in fluid systems, gauge pressure in tires and pipes, and absolute pressure which includes atmospheric contribution. Standard atmospheric pressure at sea level is 101,325 Pa (1 atm). Pressure can be measured using manometers, barometers, Bourdon tube gauges, and piezoelectric sensors. Understanding pressure is essential in meteorology, engineering, medicine, diving, aviation, and countless industrial applications.
What is the difference between absolute and gauge pressure?
Absolute pressure is measured relative to a perfect vacuum (zero pressure), while gauge pressure is measured relative to atmospheric pressure. Gauge pressure equals absolute pressure minus atmospheric pressure. When a tire gauge reads 32 psi, that is gauge pressure; the absolute pressure inside the tire is actually about 46.7 psi (32 + 14.7 psi atmospheric). In engineering, gauge pressure is denoted with a 'g' suffix (psig) and absolute with an 'a' suffix (psia). Vacuum pressures are negative gauge pressures. Most everyday pressure measurements use gauge pressure, but thermodynamic calculations and gas law equations require absolute pressure to produce correct results.
What is standard atmospheric pressure and why does it matter?
Standard atmospheric pressure is defined as exactly 101,325 pascals (1 atm), which equals 1.01325 bar, 14.696 psi, 760 mmHg, or 29.921 inches of mercury. This value represents the average sea-level pressure and serves as a reference point throughout science and engineering. It matters because many physical and chemical properties are specified at standard pressure: boiling points, gas densities, and chemical equilibrium constants. Water boils at 100 degrees Celsius only at standard pressure; at higher altitudes where pressure is lower, water boils at lower temperatures. Standard pressure is also critical for aircraft altimeter calibration and weather forecasting.
How are PSI and atmospheres related?
One atmosphere equals exactly 14.69595 PSI (pounds per square inch), and conversely one PSI equals approximately 0.06805 atmospheres. PSI is the most common pressure unit in the United States and is used for tire pressure, blood pressure monitors (in some regions), hydraulic systems, and compressed gas cylinders. Atmospheres are more commonly used in scientific contexts and diving. To convert PSI to atmospheres, divide by 14.696. For quick mental math, 15 PSI is approximately 1 atm, 30 PSI is about 2 atm, and so on. Both units are widely understood, but international engineering increasingly uses kilopascals and bars for standardization.
What is a bar and how does it relate to other pressure units?
One bar equals exactly 100,000 pascals (100 kPa) and is very close to standard atmospheric pressure (1 atm = 1.01325 bar). The bar was introduced to provide a convenient metric unit close to atmospheric pressure without the awkwardness of expressing pressure in hundreds of thousands of pascals. The millibar (1/1000 of a bar = 100 Pa = 1 hectopascal) is the traditional unit for atmospheric pressure in meteorology and weather forecasts. Many European countries use bar for tire pressure and industrial applications. The bar is not an official SI unit but is accepted for use with the SI system, making it a practical bridge between scientific and everyday pressure measurements.
What are Torr and mmHg and how are they different?
Torr and mmHg (millimeters of mercury) are nearly identical pressure units, both named in honor of Evangelista Torricelli, who invented the mercury barometer in 1644. One Torr is defined as exactly 1/760 of a standard atmosphere (133.322 Pa), while one mmHg is the pressure exerted by a 1mm column of mercury at 0 degrees Celsius under standard gravity (133.322 Pa). The difference between them is extremely small (about 0.000015 percent) and is negligible for all practical purposes. Both units are widely used in medicine for blood pressure readings (normal is about 120/80 mmHg), in vacuum technology, and in laboratory chemistry for expressing vapor pressures.
How does atmospheric pressure change with altitude?
Atmospheric pressure decreases approximately exponentially with altitude because there is less air mass above at higher elevations. The barometric formula approximates this relationship: P = P0 times (1 - Lh/T0) raised to the power gM/(RL), where L is the temperature lapse rate. As a rough guide, pressure drops about 12 Pa per meter of altitude gain near sea level (about 1 hPa per 8.5 meters). At 5,500 meters (18,000 feet), pressure is roughly half of sea level. At airplane cruising altitude of 10,000 meters, pressure is only about 26 percent of sea level. This pressure decrease is why airplane cabins are pressurized and why mountaineers need supplemental oxygen above about 8,000 meters.
What is water column pressure and when is it used?
Water column pressure (measured in cmH2O or inH2O) represents the pressure exerted by a column of water of a specified height. One centimeter of water column equals 98.0665 pascals, and one inch of water equals 249.089 pascals. These units are commonly used in HVAC systems for measuring duct pressure, in medical ventilators for airway pressure settings (typical ventilator pressures range from 5 to 40 cmH2O), and in low-pressure applications where pascal or PSI readings would be inconveniently small numbers. Water column gauges are simple, reliable, and easy to read, making them popular for applications requiring measurement of very small pressure differences.
How is pressure related to depth underwater?
Pressure increases linearly with depth underwater at a rate of approximately 9,807 pascals (about 0.1 atm or 1.47 psi) per meter of freshwater depth. In seawater, which is slightly denser, the rate is about 10,050 Pa per meter. Every 10 meters of water depth adds approximately one atmosphere of pressure. At 10 meters deep, total pressure is about 2 atm (1 atm water + 1 atm air above). At 30 meters (typical recreational diving limit), pressure is 4 atm. At the bottom of the Mariana Trench (about 11,000 meters), pressure exceeds 1,100 atm. This pressure increase is critical for scuba diving safety, submarine design, and underwater construction.
What pressure units are used in different industries?
Different industries have adopted specific pressure units based on historical convention and practical needs. Aviation uses hectopascals (hPa) and inches of mercury (inHg) for altimeter settings and weather reporting. Automotive uses PSI (US) or bar/kPa (Europe) for tire pressure. Medicine uses mmHg for blood pressure and cmH2O for ventilator settings. Meteorology uses hectopascals (millibars) for weather maps. Scuba diving uses bar or atm for tank and depth pressure. Industrial hydraulics typically uses PSI (US) or megapascals (international). Vacuum technology uses Torr, millibar, or pascal depending on the vacuum range. Understanding these conventions is essential for cross-disciplinary communication.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
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