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# UnitPressure

A unit of measure for pressure.

```
class UnitPressure
```

## Overview

You typically use instances of [`UnitPressure`](/documentation/Foundation/UnitPressure) to represent specific quantities of pressure using the [`NSMeasurement`](/documentation/Foundation/NSMeasurement) class.

### Pressure

Pressure is the normal force over a surface. The SI unit for pressure is the pascal (Pa), which is derived as one newton of force over one square meter (`1 Pa = 1 N / 1 m`2).

The [`UnitPressure`](/documentation/Foundation/UnitPressure) class defines its [`baseUnit()`](/documentation/Foundation/Dimension/baseUnit()) as [`newtonsPerMetersSquared`](/documentation/Foundation/UnitPressure/newtonsPerMetersSquared) and provides the following units, which [`UnitConverterLinear`](/documentation/Foundation/UnitConverterLinear) converters initialize with the given coefficients:

|Name                                             |Method                                                                                       |Symbol|Definition |
|-------------------------------------------------|---------------------------------------------------------------------------------------------|------|-----------|
|Newtons Per Meter Squared (Equivalent to Pascals)|``doc://com.apple.foundation/documentation/Foundation/UnitPressure/newtonsPerMetersSquared`` |N/m²  |`1.0`      |
|Gigapascals                                      |``doc://com.apple.foundation/documentation/Foundation/UnitPressure/gigapascals``             |GPa   |`1e9`      |
|Megapascals                                      |``doc://com.apple.foundation/documentation/Foundation/UnitPressure/megapascals``             |MPa   |`1000000.0`|
|Kilopascals                                      |``doc://com.apple.foundation/documentation/Foundation/UnitPressure/kilopascals``             |kPa   |`1000.0`   |
|Hectopascals                                     |``doc://com.apple.foundation/documentation/Foundation/UnitPressure/hectopascals``            |hPa   |`100.0`    |
|Inches of Mercury                                |``doc://com.apple.foundation/documentation/Foundation/UnitPressure/inchesOfMercury``         |inHg  |`3386.39`  |
|Bars                                             |``doc://com.apple.foundation/documentation/Foundation/UnitPressure/bars``                    |bar   |`100000`   |
|Millibars                                        |``doc://com.apple.foundation/documentation/Foundation/UnitPressure/millibars``               |mbar  |`100`      |
|Millimeters of Mercury                           |``doc://com.apple.foundation/documentation/Foundation/UnitPressure/millimetersOfMercury``    |mmHg  |`133.322`  |
|Pounds Per Square Inch                           |``doc://com.apple.foundation/documentation/Foundation/UnitPressure/poundsForcePerSquareInch``|psi   |`6894.76`  |

## Topics

### Accessing the Base Unit

[`baseUnit()`](/documentation/Foundation/Dimension/baseUnit())

Returns the base unit.

### Accessing Predefined Units

[`gigapascals`](/documentation/Foundation/UnitPressure/gigapascals)

The gigapascals unit of pressure.

[`megapascals`](/documentation/Foundation/UnitPressure/megapascals)

The megapascals unit of pressure.

[`kilopascals`](/documentation/Foundation/UnitPressure/kilopascals)

The kilopascals unit of pressure.

[`hectopascals`](/documentation/Foundation/UnitPressure/hectopascals)

The hectopascals unit of pressure.

[`inchesOfMercury`](/documentation/Foundation/UnitPressure/inchesOfMercury)

The inches of mercury unit of pressure.

[`bars`](/documentation/Foundation/UnitPressure/bars)

The bars unit of pressure.

[`millibars`](/documentation/Foundation/UnitPressure/millibars)

The millibars unit of pressure.

[`millimetersOfMercury`](/documentation/Foundation/UnitPressure/millimetersOfMercury)

The millimeters of mercury unit of pressure.

[`newtonsPerMetersSquared`](/documentation/Foundation/UnitPressure/newtonsPerMetersSquared)

The newtons per square meter unit of pressure.

[`poundsForcePerSquareInch`](/documentation/Foundation/UnitPressure/poundsForcePerSquareInch)

The pounds per square inch unit of pressure.


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