Issue while adding number

Question

The following code returns

SUM : 5.820766091346741E-11 instead of 0. What is the solution for this?

List<double> numbers = new List<double>();
numbers.Add(0);
numbers.Add(570056.52);
numbers.Add(0);
numbers.Add(13270);
numbers.Add(90);
numbers.Add(12565);
numbers.Add(1200);
numbers.Add(20300);
numbers.Add(39700);
numbers.Add(0);
numbers.Add(-1194861.7);
numbers.Add(2680);
numbers.Add(36977.82);
numbers.Add(155847.36);
numbers.Add(98933);
numbers.Add(141642);
numbers.Add(101600);
string numberSum = numbers.Sum(x => x).ToString();
Console.WriteLine("SUM : " + numberSum);
Console.ReadKey();

Answer 1

Hi @Samoj Bhattarai , Welcome to Microsoft Q&A.

This is due to a problem with double precision data.

Floating point numbers have limited precision and may introduce small rounding errors into calculations.

In this case the sum of the numbers should be 0, but due to rounding errors you will get a very small non-zero value.

Typically, we do some processing on the result.

For example, as below, round the data to 2 decimal places and format it as "0.00".

double sum = numbers.Sum(x => x);

double roundedSum = Math.Round(sum, 2); // Round the sum to 2 decimal places

string numberSum = roundedSum.ToString("0.00"); // Format the sum with two decimal places

Console.WriteLine("SUM : " + numberSum);

Best Regards,

Jiale

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