how to drop decimals after 3rd decimal

Question

I have a UI control which is based on a double instead of an decimal.

When it should return a value of 0.001 it returns a value of 0.00100000004749745

How do I convert this to a decimal with the correct value of 0.001?

Note that I am not trying to format it as a string, just get the correct value.

Your best bet is to start using decimal when you care about that precision. Powers of ten do not have simple representations in base-2. All of the conversions and rounding will result in error at some point. — n8wrl, Feb 20 '14 at 15:41
I agree, but the control is based on a double and I cannot rewrite the control. Thus I am converting the number before actually using it. — Greg Gum, Feb 20 '14 at 15:44

BRAHIM Kamel · Accepted Answer · 2014-02-20T15:44:04.060

3

just use Math.Round Method (Decimal, Int32)

            double d = 0.00100000004749745;
            double ma = Math.Round(d, 3);  
            //if you want it as a string 
            string s = ma.ToString();

edited Feb 20 '14 at 15:44

answered Feb 20 '14 at 15:41

BRAHIM Kamel

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I think you need to add the ToString into there so only 3 dps are shown – Liath Feb 20 '14 at 15:41

score 1 · Answer 2 · answered Feb 20 '14 at 15:41

1

double d= 0.00100000004749745;
String s=d.ToString("N3");    //gives you 0.001
decimal dd=Convert.ToDecimal(s);//converts double value 0.001 into decimal

answered Feb 20 '14 at 15:41

Sudhakar Tillapudi

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score 0 · Answer 3 · answered Feb 20 '14 at 15:42

0

try this

double d= yourNum;
String s=d.ToString("0.00");

answered Feb 20 '14 at 15:42

Aftab Ahmed

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`"0.000"` then :) And convert back to `double`. Which is pretty inefficient. – CompuChip Feb 20 '14 at 15:43
in question he is not asking for rounding he wants to get number upto two decimal places. – Aftab Ahmed Feb 20 '14 at 15:49

score 0 · Answer 4 · answered Feb 20 '14 at 15:43

0

You're experiencing the fact that 0.1 cannot be stored exactly in a double.

If you just want to display the result in 3 decimals and not worry about the floating-point error just use:

string s = dec.ToString("0.000");

answered Feb 20 '14 at 15:43

D Stanley

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score 0 · Answer 5 · edited May 23 '17 at 10:31

you can find a similar question already answered here using the String Format :

c# - How do I round a decimal value to 2 decimal places (for output on a page)

This can be a simple way to solve your problem using :

decimalVar.ToString ("#.###");

For more complex purposes this can be used if you want to keep working with a decimal value :

decimal.Round(yourValue, 3, MidpointRounding.AwayFromZero);

how to drop decimals after 3rd decimal

5 Answers5