How to Round to the Nearest 0.5

How do I round to the nearest 0.5?

Multiply your rating by 2, then round using Math.Round(rating, MidpointRounding.AwayFromZero), then divide that value by 2.

Math.Round(value * 2, MidpointRounding.AwayFromZero) / 2

How to round a decimal to the nearest 0.5 (0.5, 1.5, 2.5, 3.5)

First, you can round to integer by

let x = 1.296;
let y = Math.round(x);

Then, you can subtract 0.5 first, then round, then add 0.5

let x = 1.296;
let y = Math.round(x-0.5);
let z = y + 0.5;

How do I round to the nearest 0.5

Here's your data:

var data = new[]
{
    new { input = 10.00, expected = 10.50 },
    new { input = 10.10, expected = 10.50 },
    new { input = 10.20, expected = 10.50 },
    new { input = 10.30, expected = 10.50 },
    new { input = 10.40, expected = 10.50 },
    new { input = 10.50, expected = 10.50 },
    new { input = 10.60, expected = 11.00 },
    new { input = 10.70, expected = 11.00 },
    new { input = 10.80, expected = 11.00 },
    new { input = 10.90, expected = 11.00 },
};

The normal way to round up to the nearest 0.5 is to use Math.Ceiling(input * 2.0) / 2.0).

I would do that this way:

var output =
    data
        .Select(x => new
        {
            x.input,
            x.expected,
            actual = Math.Ceiling(x.input * 2.0) / 2.0
        });

That gives me:

I do note that 10 stays as 10 instead of 10.5 as per your requirement. I wonder if you got that requirement wrong since 10.5 doesn't round up?

Round to nearest 0.5, Not 0.0

You could add 0.5 to the value returned by Math.floor():

const round = (number) => Math.floor(number) + 0.5


console.log(round(1.0))

console.log(round(1.99))

console.log(round(2.0))

function roundHalf(num) {
    return Math.round(num*2)/2;
}

public decimal RoundToNearestHalf(this decimal value)
{
    return Math.Round(value * 2) / 2;
}

var num1 = (3.7).RoundToNearestHalf(); // 3.5
var num1 = (4.0).RoundToNearestHalf(); // 4.0

num = 3.46
result = round(num * 2) / 2
print(result)  # 3.5

def to_nearest_half(num):
    return round(num * 2) / 2

def to_nearest(num, decimal):
   return round(num / decimal) * decimal

double a = 13.1;
double rounded = Math.Ceil(a * 2) / 2;