Get the Number of Digits After the Decimal Point of a Float (With or Without Decimal Part)

How to get numbers after decimal point?

An easy approach for you:

number_dec = str(number-int(number))[1:]

Get the number of digits after the decimal point of a float (with or without decimal part)

I found some simple script (relatively to me) to handle this.

ISNULL(NULLIF(CHARINDEX('.',REVERSE(CONVERT(VARCHAR(50), Amount, 128))),0) - 1,0)

Here the ISNULL(NULLIF is only to handle the float without decimal part.
If there is no values without decimal part, then it is very simple

CHARINDEX('.',REVERSE(CONVERT(VARCHAR(50), Amount, 128))) -1 

Hope this will be helpful to you.
Full script below

declare @YourTable table (Amount float)
insert into @YourTable
values(123),(123.1),(123.0123),(123.789456)

SELECT  ISNULL(NULLIF(CHARINDEX('.',REVERSE(CONVERT(VARCHAR(50), Amount, 128))),0) - 1,0)
FROM    @YourTable

SELECT  CHARINDEX('.',REVERSE(CONVERT(VARCHAR(50), Amount, 128))) -1 
FROM    @YourTable

Get decimal portion of a number with JavaScript

Use 1, not 2.

js> 2.3 % 1
0.2999999999999998

PHP: get number of decimal digits

$str = "1.23444";
print strlen(substr(strrchr($str, "."), 1));

Finding the number of places after the decimal point of a Double

There's no easy way, especially since the number of digits mathematically speaking might be far more than displayed. For example, 4.5565 is actually stored as 4.556499999999999772626324556767940521240234375 (thanks to harold for calculating that). You're very unlikely to find a useful solution to this problem.

EDIT

You could come up with some algorithm that works like this: if, as you calculate the decimal representation, you find a certain number of 9s (or zeros) in succession, you round up (or down) to the last place before the series of 9s (or zeros) began. I suspect that you would find more trouble down that road than you would anticipate.

Getting the decimal part of a double in Swift

Without converting it to a string, you can round up to a number of decimal places like this:

let x:Double = 1234.5678
let numberOfPlaces:Double = 4.0
let powerOfTen:Double = pow(10.0, numberOfPlaces)
let targetedDecimalPlaces:Double = round((x % 1.0) * powerOfTen) / powerOfTen

Your output would be

0.5678

How to get whole and decimal part of a number?

$n = 1.25;
$whole = floor($n);      // 1
$fraction = $n - $whole; // .25

Then compare against 1/4, 1/2, 3/4, etc.

In cases of negative numbers, use this:

function NumberBreakdown($number, $returnUnsigned = false)
{
  $negative = 1;
  if ($number < 0)
  {
    $negative = -1;
    $number *= -1;
  }

  if ($returnUnsigned){
    return array(
      floor($number),
      ($number - floor($number))
    );
  }

  return array(
    floor($number) * $negative,
    ($number - floor($number)) * $negative
  );
}

The $returnUnsigned stops it from making -1.25 in to -1 & -0.25

Truncate number to two decimal places without rounding

Convert the number into a string, match the number up to the second decimal place:

function calc(theform) {    var num = theform.original.value, rounded = theform.rounded    var with2Decimals = num.toString().match(/^-?\d+(?:\.\d{0,2})?/)[0]    rounded.value = with2Decimals}

<form onsubmit="return calc(this)">Original number: <input name="original" type="text" onkeyup="calc(form)" onchange="calc(form)" /><br />"Rounded" number: <input name="rounded" type="text" placeholder="readonly" readonly></form>