rounding error

rounding error (countable and uncountable, plural rounding errors)

1. (mathematics) The difference between the result of a calculation using exact arithmetic and finite-precision, rounded arithmetic.

   Synonym: roundoff error

   The rocket's malfunction was down to a rounding error in the mathematics of its trajectory guidance.

   • 2017 February 1, Stephen Buranyi, “The high-tech war on science fraud”, in The Guardian‎:

     In an email, a computer program named Statcheck informed him that a 2013 paper he had published on multiculturalism and prejudice appeared to contain a number of incorrect calculations – which the program had catalogued and then posted on the internet for anyone to see. The problems turned out to be minor – just a few rounding errors – but the experience left Kauff feeling rattled.

2. (by extension) A negligible fraction of something.

   Coordinate term: pocket change

   In the budget of the rocket forces, the 200 thousand dollars for the investigation was a mere rounding error.

   • 2009 September 30, Bobbie Johnson, quoting Steve Ballmer, “Does Google's Chrome Frame make your PC less secure?”, in The Guardian‎:

     Microsoft's chief executive, Steve Ballmer, recently called Chrome's market share “a rounding error, to date” in an interview with TechCrunch.

   • 2017 June 27, Phillip Inman, quoting Carl Emmerson, “Extra £1bn for Northern Ireland will barely dent public finances”, in The Guardian‎:

     As Carl Emmerson, deputy head of the Institute for Fiscal Studies, said: “The size of the UK’s public finances means you can give away £1bn a year and it’s not much more than a rounding error.”

   • 2018 June 24, “There’s no panic yet: but Trump’s trade war could get out of hand”, in The Guardian‎:

     The sum of money involved is small and, compared to the trillions of dollars traded each year, almost a rounding error.

• round-off error on Wikipedia.Wikipedia