Problem with Rounding off to nearest 0.05 value

Question

There are already so many questions asked about this already.

One popular answer is to use the below formula.

  Math.ceiling(myValue * 20) / 20

I need the following output for corresponding input.

     16.489 (input)   - 16.49(output)

Using the above formula

     16.489*20  = 329.78

     Math.ceil(329.78) = 330.0

     and 330.0 /20  = 16.5

but what I want is 16.49.

Ideally the Math.ceil stuff should have given 329.8

So how do we get around the above case? There are many other cases similar to this.

16.49, rounded to the nearest 0.05, is 16.50; are you wanting a value rounded to the nearest 0.005? — supercat, Jun 13 '11 at 15:34

aioobe · Accepted Answer · 2011-06-13T15:36:39.433

Instead of multiplying / dividing with 2*10, you should do it with 10².

However, I suggest you use Math.round(100*a) / 100.0, or if you need it for printing, printf or DecimalFormat.

Examples:

double input = 16.489;

// Math.round
System.out.println(Math.round(100 * input) / 100.0);

// Decimal format
System.out.println(new DecimalFormat("#.##").format(input));

// printf
System.out.printf("%.2f", input);

Output:

16.49
16.49
16.49

RMT · Answer 2 · 2011-06-13T15:37:33.553

2

Why not use Math.round() to format your value?

edit: Math.round(value * 100.0) / 100.0;

edited Jun 13 '11 at 15:37

answered Jun 13 '11 at 15:32

RMT

7,040
4
25
37

That rounds off 0.5. He needs 0.05. – aioobe Jun 13 '11 at 15:34

score 0 · Answer 3 · edited May 23 '17 at 12:12

0

I think this would help you.This link gives you a discussion on how to round off a number to the n-th decimal place.

edited May 23 '17 at 12:12

Community

1
1

answered Jun 13 '11 at 15:38

Balanivash

6,709
9
32
48

score 0 · Answer 4 · answered Jun 13 '11 at 15:41

Rounding 16.489 up to the nearest 0.05 is correctly 16.5, with 16.45 being the next lowest possible value.

The behaviour seen is correct. If you want to be able to round up to the nearest 0.01 then

Math.ceiling(myValue * 100) / 100

would be a more appropriate solution.

score -1 · Answer 5 · edited Mar 11 '15 at 09:08

try this

round(16.489, 2, BigDecimal.ROUND_CEILING);

public static double round(double x, int scale, int roundingMethod) {
        try {
            return (new BigDecimal
                   (Double.toString(x))
                   .setScale(scale, roundingMethod))
                   .doubleValue();
        } catch (NumberFormatException ex) {
            if (Double.isInfinite(x)) {
                return x;
            } else {
                return Double.NaN;
            }
        }
    }

Problem with Rounding off to nearest 0.05 value

5 Answers5