# Difference Between PSI And PSIG

##### Knowledgebase

Last Updated on April 15, 2023 by mdmtool

PSI (Pounds per Square Inch) and PSIG (Pounds per Square Inch Gauge) are two widely used measurements to measure pressure. Both PSI and PSIG indicate the amount of force exerted on a single square inch of an area. However, there is a subtle difference between PSI and PSIG.

The major difference between the two units of measurement lies in the reference pressure used for calculation. While PSI indicates the absolute pressure, PSIG indicates the gauge pressure. In other words, while calculating pressure using PSI measurements, atmospheric pressure is taken into consideration as it adds to the total pressure. On the other hand, PSIG is only concerned with the difference between absolute pressure and atmospheric pressure.

## PSI VS PSIG

### What Is PSI, And Why Is It Important?

– PSI stands for Pounds per Square Inch and is an important unit of measurement used to measure pressure. It measures the amount of force exerted on a single square inch of area.

### What Is PSIG, And Why Is It Important?

– PSIG stands for Pounds per Square Inch Gauge and is a unit of measurement used to measure pressure. It measures the difference between absolute pressure and atmospheric pressure, i.e., it indicates the gauge pressure.

### Where Is It Used?

PSI: It is widely used in the field of engineering. It is also used to measure fuel pressure, air pressure, water pressure, and tire pressure.

PSIG: It is mostly used for measuring steam or gas pressure in closed systems. It can also be used in laboratories to measure the pressure of a sealed container.

### Do PSI And PSIG Mean The Same Thing?

– No, PSI and PSIG are not the same. While PSI indicates absolute pressure, PSIG measures gauge pressure. Atmospheric pressure is taken into account when calculating PSI, whereas it is ignored in the case of PSIG calculations. Thus, a difference exists between these two units of measurement.

### How To Convert PSIG to PSI?

The most common way to convert PSIG (pounds per square inch gauge) to PSI (pounds per square inch absolute) is by subtracting atmospheric pressure from the PSIG reading. Atmospheric pressure at sea level equals 14.7 psi. To convert PSIG to PSI, simply subtract 14.7 from the given PSIG reading. For example, if a pressure gauge reads 57 PSIG, the absolute pressure would be 42.3 PSI (57-14.7=42.3).

### How To Convert PSI to PSIG?

To convert PSI to PSIG, simply add atmospheric pressure (14.7 psi) to the given PSI reading. For example, if a pressure gauge reads 30 PSI, the gauge pressure would be 44.7 PSIG (30+14.7=44.7). It is important to note that atmospheric pressure, when converting between PSI and PSIG, is always 14.7 psi at sea level.

## Similarities Between PSI and PSIG

1. Both PSI and PSIG measure pressure.
2. They both indicate the amount of force exerted on a single square inch of an area.
3. They are both widely used for measuring different types of pressure in engineering, laboratories, and other fields.
4. To convert between PSI and PSIG, atmospheric pressure is taken into account.

### FACTORS Influencing PSI AND PSIG:

1. Temperature: Pressure is affected by temperature changes. As temperature increases, pressure decreases, and vice versa.
2. Altitude: Atmospheric pressure decreases with altitude, and so does the PSI value.
3. Moisture: Moisture in the air can affect pressure readings, as humidity can lead to higher pressure readings.
4. Air Density: The density of the air affects the pressure readings, as more dense air will lead to higher pressure readings.
5. Wind: Wind can cause changes in pressure, as the rapid movement of air can lead to pressure fluctuations.

## Difference Between PSI and PSIG

Basics of PSI and PSIG:

• PSI: Pounds per Square Inch (PSI) is the standard unit of measurement for pressure. It measures the amount of force that is applied to an area and is expressed as a ratio of pounds force per square inch.
• PSIG: Pounds per Square Inch Gauge (PSIG) is a unit of pressure measurement that indicates the amount of force applied to a certain area. PSIG measurements are expressed as a ratio of pounds-force per square inch and take into account the atmospheric pressure of a given location.

Calculation of PSI and PSIG:

• PSI: PSI can be calculated by dividing the force applied to an area, in pounds-force (lbf), by the area, in square inches (in2).
• PSIG: PSIG is calculated by adding atmospheric pressure to the PSI measurement. The atmospheric pressure at a certain location can be calculated by subtracting the PSI measurement from 14.7, or the standard atmospheric pressure.

Applications of PSI and PSIG:

PSI:

• Used to measure the pressure of liquids and gases.
• Used in many fields, such as engineering, medicine, and automotive.
• Commonly found in tire pressure measurements.

PSIG:

• used to measure the pressure of liquids and gases that are exposed to atmospheric pressure.
• common applications include air compressors, boilers, and pumps.
• also used in tire pressure measurements.

1. Easier to use than PSIG as it does not require any calculations.

2. Can be used universally regardless of atmospheric pressure.

3. Wide range of applications across industries, from engineering and automotive to medicine.

1. Does not take into consideration the atmospheric pressure of a location.

2. Not accurate in determining the pressure of liquids and gases exposed to atmospheric pressure.

1. More accurate than PSI as it takes into account the atmospheric pressure of a location.

2. Can be used for liquids and gases that are exposed to atmospheric pressure, such as air compressors, boilers and pumps.

3. Also used for tire pressure measurements.

1. Requires calculations to determine the PSIG value which may be more complicated than calculating the PSI value.

2. Not suitable for all applications due to its inability to measure the pressure of liquids and gases that are not exposed to atmospheric pressure.

3. Not widely used across different industries other than engineering, automotive and medicine.

### What Is Atmospheric Pressure?

Atmospheric pressure is defined as the force per unit area exerted on an object by the atmosphere. It is typically measured in pounds per square inch (psi) or hectopascals (hPa). The atmospheric pressure at sea level is 14.7 psi or 1013.25 hPa.

### How Is Atmospheric Pressure Measured?

Atmospheric pressure is typically measured by a barometer or an instrument known as a manometer. The most common unit for measuring atmospheric pressure is pounds per square inch (psi). It can also be measured in inches of mercury, hectopascals (hPa), millibars, and others.

### What Does 0 PSIG Mean?

0 PSIG means zero pounds per square inch gauge, which is the same as atmospheric pressure. This means that the pressure at a certain location is equal to the atmospheric pressure of that location. In order for a reading to be taken in terms of PSIG, atmospheric pressure must be taken into account.

### What Is 14.7 PSI In Atmospheric Pressure?

14.7 PSI is equal to the atmospheric pressure at sea level, which is 1013.25 hPa or 14.7 psi. This means that the atmospheric pressure at any given location, when measured in pounds per square inch (psi), will be equal to 14.7 psi.

### What Is 5 Bar Equal To In PSI?

5 bar is equal to 72.5 psi, which is calculated by multiplying 5 bar by 14.7 psi (the atmospheric pressure at sea level). This means that the pressure at a certain location in terms of the bar can be converted to pounds per square inch (psi) by multiplying it by 14.7 psi.

### Who Uses Bar Instead Of PSI?

The bar is used in many industries, such as engineering, automotive, and medicine. It is also commonly found in tire pressure measurements. The bar is a metric unit of pressure and is understood to be slightly more precise than PSI, which is why it is sometimes preferred over psi by certain professionals.

### Why Is Bar Used Instead Of PSI?

The bar is a metric unit of pressure and is understood to be slightly more precise than PSI. This means that it can provide more accurate readings in certain applications, such as tire pressure measurements or measuring the pressure of liquids and gases exposed to atmospheric pressure. Therefore, the bar may be preferred over psi by certain professionals for these types of measurements.

### Do Americans Use Bar Or PSI?

Both bar and psi are used in the United States, but psi is more commonly used due to its simplicity. Many industries use psi for measuring pressure, as it is easier to calculate with than bar. However, certain professionals may prefer to use bar due to its higher level of accuracy in certain applications.

### Why Is Pressure Called Bar?

The term “bar” is derived from the Greek word baros, which means weight. This reflects the fact that bar is a unit of pressure and is measured in terms of force per unit area.

### Does PSI Mean PSIA Or PSIG?

PSI can mean either PSIA (Pounds per Square Inch Absolute) or PSIG (Pounds per Square Inch Gauge). PSIA is referenced to a perfect vacuum, while PSIG is referenced to atmospheric pressure. So if you are measuring the pressure of something relative to atmospheric pressure, then it would be measured in terms of PSIG. However, if you are measuring the absolute pressure of something, then it would be measured in terms of PSIA.

## Conclusion

PSI and PSIG are both units of measurement that are used to measure the pressure of liquids and gases. The main difference between the two is that PSI measures pressure independent of atmospheric pressure, while PSIG measures the pressure taking into account atmospheric pressure. Both can be calculated by dividing the force applied to an area, in pounds-force (lbf), by the area, in square inches (in2). They are both commonly used in many fields such as engineering, medicine, and automotive, as well as tire pressure measurements. Consequently, it is important for users to understand the difference between PSI and PSIG to ensure accurate measurements.

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