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round

(PHP 4, PHP 5, PHP 7, PHP 8)

round —Rounds a float

Description

round(int|float$num,int$precision = 0,int|RoundingMode$mode = RoundingMode::HalfAwayFromZero):float

Returns the rounded value ofnum to specifiedprecision (number of digits after the decimal point).precision can also be negative or zero (default).

Parameters

num

The value to round.

precision

The optional number of decimal digits to round to.

If theprecision is positive,num is rounded toprecision significant digits after the decimal point.

If theprecision is negative,num is rounded toprecision significant digits before the decimal point, i.e. to the nearest multiple ofpow(10, -$precision), e.g. for aprecision of -1num is rounded to tens, for aprecision of -2 to hundreds, etc.

mode

UseRoundingMode or one of the following constants to specify the mode in which rounding occurs.

Constants	Description
`PHP_ROUND_HALF_UP`	Rounds`num` away from zero when it is half way there, making 1.5 into 2 and -1.5 into -2.
`PHP_ROUND_HALF_DOWN`	Rounds`num` towards zero when it is half way there, making 1.5 into 1 and -1.5 into -1.
`PHP_ROUND_HALF_EVEN`	Rounds`num` towards the nearest even value when it is half way there, making both 1.5 and 2.5 into 2.
`PHP_ROUND_HALF_ODD`	Rounds`num` towards the nearest odd value when it is half way there, making 1.5 into 1 and 2.5 into 3.

However, please note that some newly added modes only exist inRoundingMode.

Return Values

The value rounded to the givenprecision as afloat.

Errors/Exceptions

The function throws aValueError ifmode is invalid. Prior to PHP 8.4.0, an invalid mode would silently default toPHP_ROUND_HALF_UP.

Changelog

Version	Description
8.4.0	Four new rounding modes have been added.
8.4.0	Now throws aValueError if`mode` is invalid.
8.0.0	`num` no longer accepts internal objects which support numeric conversion.

Examples

Example #1round() examples

<?php
var_dump(round(3.4));
var_dump(round(3.5));
var_dump(round(3.6));
var_dump(round(3.6,0));
var_dump(round(5.045,2));
var_dump(round(5.055,2));
var_dump(round(345, -2));
var_dump(round(345, -3));
var_dump(round(678, -2));
var_dump(round(678, -3));
?>

The above example will output:

float(3)float(4)float(4)float(4)float(5.05)float(5.06)float(300)float(0)float(700)float(1000)

Example #2 Howprecision affects a float

<?php
$number=135.79;

var_dump(round($number,3));
var_dump(round($number,2));
var_dump(round($number,1));
var_dump(round($number,0));
var_dump(round($number, -1));
var_dump(round($number, -2));
var_dump(round($number, -3));
?>

The above example will output:

float(135.79)float(135.79)float(135.8)float(136)float(140)float(100)float(0)

Example #3mode examples

<?php
echo'Rounding modes with 9.5'.PHP_EOL;
var_dump(round(9.5,0,PHP_ROUND_HALF_UP));
var_dump(round(9.5,0,PHP_ROUND_HALF_DOWN));
var_dump(round(9.5,0,PHP_ROUND_HALF_EVEN));
var_dump(round(9.5,0,PHP_ROUND_HALF_ODD));

echoPHP_EOL;
echo'Rounding modes with 8.5'.PHP_EOL;
var_dump(round(8.5,0,PHP_ROUND_HALF_UP));
var_dump(round(8.5,0,PHP_ROUND_HALF_DOWN));
var_dump(round(8.5,0,PHP_ROUND_HALF_EVEN));
var_dump(round(8.5,0,PHP_ROUND_HALF_ODD));
?>

The above example will output:

Rounding modes with 9.5float(10)float(9)float(10)float(9)Rounding modes with 8.5float(9)float(8)float(8)float(9)

Example #4mode withprecision examples

<?php
echo'Using PHP_ROUND_HALF_UP with 1 decimal digit precision'.PHP_EOL;
var_dump(round(1.55,1,PHP_ROUND_HALF_UP));
var_dump(round(-1.55,1,PHP_ROUND_HALF_UP));

echoPHP_EOL;
echo'Using PHP_ROUND_HALF_DOWN with 1 decimal digit precision'.PHP_EOL;
var_dump(round(1.55,1,PHP_ROUND_HALF_DOWN));
var_dump(round(-1.55,1,PHP_ROUND_HALF_DOWN));

echoPHP_EOL;
echo'Using PHP_ROUND_HALF_EVEN with 1 decimal digit precision'.PHP_EOL;
var_dump(round(1.55,1,PHP_ROUND_HALF_EVEN));
var_dump(round(-1.55,1,PHP_ROUND_HALF_EVEN));

echoPHP_EOL;
echo'Using PHP_ROUND_HALF_ODD with 1 decimal digit precision'.PHP_EOL;
var_dump(round(1.55,1,PHP_ROUND_HALF_ODD));
var_dump(round(-1.55,1,PHP_ROUND_HALF_ODD));
?>

The above example will output:

Using PHP_ROUND_HALF_UP with 1 decimal digit precisionfloat(1.6)float(-1.6)Using PHP_ROUND_HALF_DOWN with 1 decimal digit precisionfloat(1.5)float(-1.5)Using PHP_ROUND_HALF_EVEN with 1 decimal digit precisionfloat(1.6)float(-1.6)Using PHP_ROUND_HALF_ODD with 1 decimal digit precisionfloat(1.5)float(-1.5)

Example #5 Example of usingRoundingMode

<?php
foreach (RoundingMode::cases() as$mode) {
    foreach ([
8.5,
9.5,
        -3.5,
    ] as$number) {
printf("%-17s: %+.17g -> %+.17g\n",$mode->name,$number,round($number,0,$mode));
    }
    echo"\n";
}
?>

The above example will output:

HalfAwayFromZero : +8.5 -> +9HalfAwayFromZero : +9.5 -> +10HalfAwayFromZero : -3.5 -> -4HalfTowardsZero  : +8.5 -> +8HalfTowardsZero  : +9.5 -> +9HalfTowardsZero  : -3.5 -> -3HalfEven         : +8.5 -> +8HalfEven         : +9.5 -> +10HalfEven         : -3.5 -> -4HalfOdd          : +8.5 -> +9HalfOdd          : +9.5 -> +9HalfOdd          : -3.5 -> -3TowardsZero      : +8.5 -> +8TowardsZero      : +9.5 -> +9TowardsZero      : -3.5 -> -3AwayFromZero     : +8.5 -> +9AwayFromZero     : +9.5 -> +10AwayFromZero     : -3.5 -> -4NegativeInfinity : +8.5 -> +8NegativeInfinity : +9.5 -> +9NegativeInfinity : -3.5 -> -4PositiveInfinity : +8.5 -> +9PositiveInfinity : +9.5 -> +10PositiveInfinity : -3.5 -> -3

See Also

ceil() - Round fractions up
floor() - Round fractions down
number_format() - Format a number with grouped thousands

Found A Problem?

Learn How To Improve This Page •Submit a Pull Request •Report a Bug

User Contributed Notes13 notes

327

takingsides at gmail dot com ¶

11 years ago

In my opinion this function lacks two flags:

- PHP_ROUND_UP - Always round up.
- PHP_ROUND_DOWN - Always round down.

In accounting, it's often necessary to always round up, or down to a precision of thousandths.

<?php
functionround_up($number,$precision=2)
{
$fig= (int)str_pad('1',$precision,'0');
    return (ceil($number*$fig) /$fig);
}

functionround_down($number,$precision=2)
{
$fig= (int)str_pad('1',$precision,'0');
    return (floor($number*$fig) /$fig);
}
?>

33

depaula at unilogica dot com ¶

8 years ago

As PHP doesn't have a a native number truncate function, this is my solution - a function that can be usefull if you need truncate instead round a number.

<?php
/**
 * Truncate a float number, example: <code>truncate(-1.49999, 2); // returns -1.49
 * truncate(.49999, 3); // returns 0.499
 * </code>
 * @param float $val Float number to be truncate
 * @param int f Number of precision
 * @return float
 */
functiontruncate($val,$f="0")
{
    if(($p=strpos($val,'.')) !==false) {
$val=floatval(substr($val,0,$p+1+$f));
    }
    return$val;
}
?>

Originally posted inhttp://stackoverflow.com/a/12710283/1596489

31

slimusgm at gmail dot com ¶

10 years ago

If you have negative zero and you need return positive number simple add +0:

$number = -2.38419e-07;
var_dump(round($number,1));//float(-0)
var_dump(round($number,1) + 0);//float(0)

20

esion99 at gmail dot com ¶

11 years ago

Unexpected result or misunderstanding (php v5.5.9)

<?php

echoround(1.55,1,PHP_ROUND_HALF_DOWN);// 1.5
echoround(1.551,1,PHP_ROUND_HALF_DOWN);//1.6

?>

21

djcox99 at googlemail dot com ¶

11 years ago

I discovered that under some conditions you can get rounding errors with round when converting the number to a string afterwards.

To fix this I swapped round() for number_format().

Unfortunately i cant give an example (because the number cant be represented as a string !)

essentially I had round(0.688888889,2);

which would stay as 0.68888889 when printed as a string.

But using number_format it correctly became 0.69.

10

craft at ckdevelop dot org ¶

11 years ago

function mround($val, $f=2, $d=6){
    return sprintf("%".$d.".".$f."f", $val);
}

echo mround(34.89999);  //34.90

17

Anonymous ¶

14 years ago

Here is function that rounds to a specified increment, but always up. I had to use it for price adjustment that always went up to $5 increments.

<?php
functionroundUpTo($number,$increments) {
$increments=1/$increments;
    return (ceil($number*$increments) /$increments);
}
?>

18

twan at ecreation dot nl ¶

25 years ago

If you'd only want to round for displaying variables (not for calculating on the rounded result) then you should use printf with the float:

<?php printf("%6.2f",3.39532);?>

This returns: 3.40 .

8

christian at deligant dot net ¶

13 years ago

this function (as all mathematical operators) takes care of the setlocale setting, resulting in some weirdness when using the result where the english math notation is expected, as the printout of the result in a width: style attribute!

<?php
$a=3/4;
echoround($a,2);// 0.75

setlocale(LC_ALL,'it_IT@euro','it_IT','it');
$b=3/4;
echoround($b,2);// 0,75
?>

7

michaeldnelson dot mdn at gmail dot com ¶

15 years ago

This function will let you round to an arbitrary non-zero number.  Zero of course causes a division by zero.

<?php
functionroundTo($number,$to){
    returnround($number/$to,0)*$to;
}

echoroundTo(87.23,20);//80
echoroundTo(-87.23,20);//-80
echoroundTo(87.23,.25);//87.25
echoroundTo(.23,.25);//.25
?>

3

greghenle at gmail dot com ¶

8 years ago

/**
 * Round to first significant digit
 * +N to +infinity
 * -N to -infinity
 *
 */
function round1stSignificant ( $N ) {
  if ( $N === 0 ) {
    return 0;
  }

  $x = floor ( log10 ( abs( $N ) ) );

  return ( $N > 0 )
    ? ceil( $N * pow ( 10, $x * -1 ) ) * pow( 10, $x )
    : floor( $N * pow ( 10, $x * -1 ) ) * pow( 10, $x );
}

echo round1stSignificant( 39144818 ) . PHP_EOL;
echo round1stSignificant( 124818 ) . PHP_EOL;
echo round1stSignificant( 0.07468 ) . PHP_EOL;
echo round1stSignificant( 0 ) . PHP_EOL;
echo round1stSignificant( -0.07468 ) . PHP_EOL;

/**
 * Output
 *
 * 40000000
 * 200000
 * 0.08
 * 0
 * -0.08
 *
 */

4

dastra ¶

13 years ago

round() will sometimes return E notation when rounding a float when the amount is small enough - seehttps://bugs.php.net/bug.php?id=44223 .  Apparently it's a feature.

To work around this "feature" when converting to a string, surround your round statement with an sprintf:

sprintf("%.10f", round( $amountToBeRounded, 10));

9

php at silisoftware dot com ¶

22 years ago

Here's a function to round to an arbitary number of significant digits. Don't confuse it with rounding to a negative precision - that counts back from the decimal point, this function counts forward from the Most Significant Digit.

ex:

<?php
round(1241757, -3);// 1242000
RoundSigDigs(1241757,3);// 1240000
?>

Works on negative numbers too. $sigdigs should be >= 0

<?php
functionRoundSigDigs($number,$sigdigs) {
$multiplier=1;
    while ($number<0.1) {
$number*=10;
$multiplier/=10;
    }
    while ($number>=1) {
$number/=10;
$multiplier*=10;
    }
    returnround($number,$sigdigs) *$multiplier;
}
?>

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