Wolfram Language & System 10.3 (2015)|Legacy Documentation

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gives the effective number of digits of precision in the number x.


  • 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.
Introduced in 1988
| Updated in 2003