# Wolfram Language & System 10.4 (2016)|Legacy Documentation

This is documentation for an earlier version of the Wolfram Language.
BUILT-IN WOLFRAM LANGUAGE SYMBOL

# Precision

Precision[x]
gives the effective number of digits of precision in the number x.

## DetailsDetails

• Precision[x] gives a measure of the relative uncertainty in the value of x.
• With absolute uncertainty dx, Precision[x] is -Log[10,dx/x].
• For exact numbers such as integers, Precision[x] is Infinity.
• Precision[x] does not normally yield an integer result.
• For any approximate number x, Precision[x] is equal to RealExponent[x]+Accuracy[x].
• For machineprecision numbers, Precision[x] yields MachinePrecision.
• Numbers entered in the form are taken to have precision p.
• Numbers such as 0``a whose overall scale cannot be determined are treated as having zero precision.
• Numbers with zero precision are output in StandardForm as , where a is their accuracy.
• If x is not a number, Precision[x] gives the minimum value of Precision for all the numbers that appear in x. MachinePrecision is considered smaller than any explicit precision.

## ExamplesExamplesopen allclose all

### Basic Examples  (3)Basic Examples  (3)

Machine-precision number:

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Arbitrary-precision number:

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Exact number:

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## TutorialsTutorials

Introduced in 1988
(1.0)
| Updated in 2003
(5.0)