# NSDecimalAdd(_:_:_:_:) Adds two decimal values. ``` func NSDecimalAdd(_ result: UnsafeMutablePointer, _ leftOperand: UnsafePointer, _ rightOperand: UnsafePointer, _ roundingMode: NSDecimalNumber.RoundingMode) -> NSDecimalNumber.CalculationError ``` ## Discussion Adds `leftOperand` to `rightOperand` and stores the sum in `result`. [`Decimal`](/documentation/Foundation/Decimal) instances can represent a number with up to 38 significant digits. If a number is more precise than that, it must be rounded off. `roundingMode` determines how to round it off. There are four possible rounding modes: - [`NSDecimalNumber.RoundingMode.down`](/documentation/Foundation/NSDecimalNumber/RoundingMode/down) - [`NSDecimalNumber.RoundingMode.up`](/documentation/Foundation/NSDecimalNumber/RoundingMode/up) - [`NSDecimalNumber.RoundingMode.plain`](/documentation/Foundation/NSDecimalNumber/RoundingMode/plain) - [`NSDecimalNumber.RoundingMode.bankers`](/documentation/Foundation/NSDecimalNumber/RoundingMode/bankers) The return value indicates whether any machine limitations were encountered in the addition. If none were encountered, the function returns `NSCalculationNoError`. Otherwise it may return one of the following values: `NSCalculationLossOfPrecision`, `NSCalculationOverflow` or `NSCalculationUnderflow`. For descriptions of all these error conditions, see [`exceptionDuringOperation(_:error:leftOperand:rightOperand:)`](/documentation/Foundation/NSDecimalNumberBehaviors/exceptionDuringOperation(_:error:leftOperand:rightOperand:)) in NSDecimalNumberBehaviors. For more information, see [Number and Value Programming Topics](https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/NumbersandValues/NumbersandValues.html#//apple_ref/doc/uid/10000038i). --- 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)