# NSDecimalNumber An object for representing and performing arithmetic on base-10 numbers. ``` class NSDecimalNumber ``` ## Overview In Swift, this object bridges to [`Decimal`](/documentation/Foundation/Decimal); use [`NSDecimalNumber`](/documentation/Foundation/NSDecimalNumber) when you need reference semantics or other Foundation-specific behavior. `NSDecimalNumber`, an immutable subclass of `NSNumber`, provides an object-oriented wrapper for doing base-10 arithmetic. An instance can represent any number that can be expressed as `mantissa x 10^exponent` where mantissa is a decimal integer up to 38 digits long, and exponent is an integer from –128 through 127. > Important: > The Swift overlay to the Foundation framework provides the ``doc://com.apple.foundation/documentation/Foundation/Decimal`` structure, which bridges to the ``doc://com.apple.foundation/documentation/Foundation/NSDecimalNumber`` class. For more information about value types, see . ## Topics ### Creating a Decimal Number [`decimalNumberWithDecimal:`](/documentation/Foundation/NSDecimalNumber/decimalNumberWithDecimal:) Creates and returns a decimal number equivalent to a given decimal structure. [`decimalNumberWithMantissa:exponent:isNegative:`](/documentation/Foundation/NSDecimalNumber/decimalNumberWithMantissa:exponent:isNegative:) Creates and returns a decimal number equivalent to the number specified by the arguments. [`decimalNumberWithString:`](/documentation/Foundation/NSDecimalNumber/decimalNumberWithString:) Creates a decimal number whose value is equivalent to that in a given numeric string. [`decimalNumberWithString:locale:`](/documentation/Foundation/NSDecimalNumber/decimalNumberWithString:locale:) Creates a decimal number whose value is equivalent to that in a given numeric string, interpreted using a given locale. [`one`](/documentation/Foundation/NSDecimalNumber/one) A decimal number equivalent to the number 1.0. [`zero`](/documentation/Foundation/NSDecimalNumber/zero) A decimal number equivalent to the number 0.0. [`notANumber`](/documentation/Foundation/NSDecimalNumber/notANumber) A decimal number that specifies no number. ### Initializing a Decimal Number [`init(decimal:)`](/documentation/Foundation/NSDecimalNumber/init(decimal:)) Initializes a decimal number to represent a given decimal. [`init(mantissa:exponent:isNegative:)`](/documentation/Foundation/NSDecimalNumber/init(mantissa:exponent:isNegative:)) Initializes a decimal number using the given mantissa, exponent, and sign. [`init(string:)`](/documentation/Foundation/NSDecimalNumber/init(string:)) Initializes a decimal number so that its value is equivalent to that in a given numeric string. [`init(string:locale:)`](/documentation/Foundation/NSDecimalNumber/init(string:locale:)) Initializes a decimal number so that its value is equivalent to that in a given numeric string, interpreted using a given locale. ### Performing Arithmetic [`adding(_:)`](/documentation/Foundation/NSDecimalNumber/adding(_:)) Adds this number to another given number. [`subtracting(_:)`](/documentation/Foundation/NSDecimalNumber/subtracting(_:)) Subtracts another given number from this one. [`multiplying(by:)`](/documentation/Foundation/NSDecimalNumber/multiplying(by:)) Multiplies the number by another given number. [`dividing(by:)`](/documentation/Foundation/NSDecimalNumber/dividing(by:)) Divides the number by another given number. [`raising(toPower:)`](/documentation/Foundation/NSDecimalNumber/raising(toPower:)) Raises the number to a given power. [`multiplying(byPowerOf10:)`](/documentation/Foundation/NSDecimalNumber/multiplying(byPowerOf10:)) Multiplies the number by 10 raised to the given power. [`adding(_:withBehavior:)`](/documentation/Foundation/NSDecimalNumber/adding(_:withBehavior:)) Adds this number to another given number using the specified behavior. [`subtracting(_:withBehavior:)`](/documentation/Foundation/NSDecimalNumber/subtracting(_:withBehavior:)) Subtracts this a given number from this one using the specified behavior. [`multiplying(by:withBehavior:)`](/documentation/Foundation/NSDecimalNumber/multiplying(by:withBehavior:)) Multiplies this number by another given number using the specified behavior. [`dividing(by:withBehavior:)`](/documentation/Foundation/NSDecimalNumber/dividing(by:withBehavior:)) Divides this number by another given number using the specified behavior. [`raising(toPower:withBehavior:)`](/documentation/Foundation/NSDecimalNumber/raising(toPower:withBehavior:)) Raises the number to a given power using the specified behavior. [`multiplying(byPowerOf10:withBehavior:)`](/documentation/Foundation/NSDecimalNumber/multiplying(byPowerOf10:withBehavior:)) Multiplies the number by 10 raised to the given power using the specified behavior. ### Rounding Off [`rounding(accordingToBehavior:)`](/documentation/Foundation/NSDecimalNumber/rounding(accordingToBehavior:)) Returns a rounded version of the decimal number using the specified rounding behavior. ### Managing Behavior [`defaultBehavior`](/documentation/Foundation/NSDecimalNumber/defaultBehavior) The way arithmetic methods round off and handle error conditions. [`NSDecimalNumberBehaviors`](/documentation/Foundation/NSDecimalNumberBehaviors) A protocol that declares three methods that control the discretionary aspects of working with decimal numbers. [`NSDecimalNumberHandler`](/documentation/Foundation/NSDecimalNumberHandler) A class that adopts the decimal number behaviors protocol. ### Accessing the Value [`decimalValue`](/documentation/Foundation/NSDecimalNumber/decimalValue) The decimal number’s value, expressed as an [`Decimal`](/documentation/Foundation/Decimal) structure. [`doubleValue`](/documentation/Foundation/NSDecimalNumber/doubleValue) The decimal number’s closest approximate `double` value. [`description(withLocale:)`](/documentation/Foundation/NSDecimalNumber/description(withLocale:)) Returns a string representation of the decimal number appropriate for the specified locale. [`objCType`](/documentation/Foundation/NSDecimalNumber/objCType) A C string containing the Objective-C type for the data contained in the decimal number object. ### Comparing Decimal Numbers [`compare(_:)`](/documentation/Foundation/NSDecimalNumber/compare(_:)) Compares this decimal number and another. ### Getting Maximum and Minimum Possible Values [`maximum`](/documentation/Foundation/NSDecimalNumber/maximum) Returns the largest possible value of a decimal number. [`minimum`](/documentation/Foundation/NSDecimalNumber/minimum) Returns the smallest possible value of a decimal number. ### Recognizing Exceptions Exceptions with these names may be raised to indicate computational errors with decimal numbers. [`decimalNumberExactnessException`](/documentation/Foundation/NSExceptionName/decimalNumberExactnessException) The exception raised if there is an exactness error. [`decimalNumberOverflowException`](/documentation/Foundation/NSExceptionName/decimalNumberOverflowException) The exception raised on overflow. [`decimalNumberUnderflowException`](/documentation/Foundation/NSExceptionName/decimalNumberUnderflowException) The exception raised on underflow. [`decimalNumberDivideByZeroException`](/documentation/Foundation/NSExceptionName/decimalNumberDivideByZeroException) The exception raised on divide by zero. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)