round

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

round — Округляет число с плавающей точкой

Описание

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

Функция возвращает значение числа num, которое округлила с точностью precision — количество цифр после запятой. Значение точности precision принимает отрицательные значения и ноль — значение по умолчанию.

Список параметров

num

Значение, которое требуется округлить.

precision

Необязательное количество десятичных знаков, до которых функция округлит число.

Функция округлит число num до такого количества значащих цифр после десятичной точки, которое указали в параметре precision, если точность precision положительна.

Функция округлит число num до такого количества значащих цифр перед десятичной точкой, которое указали в параметре precision, если точность precision отрицательна. При отрицательном значении точности функция округляет число до следующего кратного результата выражения pow(10, -$precision). Число num округляется до десятков, если точность precision равна -1, до сотен, если точность precision равна -2, и т. д.

mode

Режим округления устанавливают константой из следующего списка:

Константы	Описание
`PHP_ROUND_HALF_UP`	Округляет положительное число `num` в бо́льшую сторону, а отрицательное в меньшую, превращая 1.5 в 2 и -1.5 в -2; стремится от нуля.
`PHP_ROUND_HALF_DOWN`	Округляет положительное число `num` в меньшую сторону, а отрицательное в бо́льшую, превращая 1.5 в 1 и -1.5 в -1; стремится к нулю.
`PHP_ROUND_HALF_EVEN`	Округляет число `num` до ближайшего чётного значения, превращая 1.5 и 2.5 в 2.
`PHP_ROUND_HALF_ODD`	Округляет число `num` до ближайшего нечётного значения, превращая 1.5 в 1 и 2.5 в 3.

Возвращаемые значения

Функция возвращает число с плавающей точкой (float), которое получила путём округления входного числа до точности, которую установили в параметре precision.

Ошибки

При недопустимом режиме mode функция выбрасывает ошибку ValueError. До PHP 8.4.0 для недопустимого режима без предупреждения устанавливалось значение PHP_ROUND_HALF_UP.

Список изменений

Версия	Описание
8.4.0	Функция теперь выбрасывает ошибку ValueError, если в параметр `mode` передали недопустимый режим округления.
8.0.0	Параметр `num` больше не принимает внутренние объекты, которые поддерживают числовое преобразование.

Примеры

Пример #1 Пример округления чисел функцией round()

<?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));

?>

Результат выполнения приведённого примера:

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

Пример #2 Пример влияния параметра precision на числа с плавающей точкой

<?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));

?>

Результат выполнения приведённого примера:

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

Пример #3 Пример влияния режима mode на округление чисел

<?php

echo 'Режимы округления с 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));

echo PHP_EOL;
echo 'Режимы округления с 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));

?>

Результат выполнения приведённого примера:

Режимы округления с 9.5
float(10)
float(9)
float(10)
float(9)

Режимы округления с 8.5
float(9)
float(8)
float(8)
float(9)

Пример #4 Пример округления чисел с режимом mode и точностью precision

<?php

echo 'Округление с точностью до 1 знака в режиме PHP_ROUND_HALF_UP' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_UP));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_UP));

echo PHP_EOL;
echo 'Округление с точностью до 1 знака в режиме PHP_ROUND_HALF_DOWN' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_DOWN));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_DOWN));

echo PHP_EOL;
echo 'Округление с точностью до 1 знака в режиме PHP_ROUND_HALF_EVEN' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_EVEN));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_EVEN));

echo PHP_EOL;
echo 'Округление с точностью до 1 знака в режиме PHP_ROUND_HALF_ODD' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_ODD));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_ODD));

?>

Результат выполнения приведённого примера:

Округление с точностью до 1 знака в режиме PHP_ROUND_HALF_UP
float(1.6)
float(-1.6)

Округление с точностью до 1 знака в режиме PHP_ROUND_HALF_DOWN
float(1.5)
float(-1.5)

Округление с точностью до 1 знака в режиме PHP_ROUND_HALF_EVEN
float(1.6)
float(-1.6)

Округление с точностью до 1 знака в режиме PHP_ROUND_HALF_ODD
float(1.5)
float(-1.5)

Смотрите также

ceil() - Округляет дробное число в бо́льшую сторону
floor() - Округляет дробное число в меньшую сторону
number_format() - Форматирует число с группировкой классов многозначного числа

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Примечания пользователей 29 notes

down

319

takingsides at gmail dot com ¶

10 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
function round_up($number, $precision = 2)
{
    $fig = (int) str_pad('1', $precision, '0');
    return (ceil($number * $fig) / $fig);
}

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

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depaula at unilogica dot com ¶

7 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 $val Float number to be truncate
 * @param int f Number of precision
 * @return float
 */
function truncate($val, $f="0")
{
    if(($p = strpos($val, '.')) !== false) {
        $val = floatval(substr($val, 0, $p + 1 + $f));
    }
    return $val;
}
?>

Originally posted in http://stackoverflow.com/a/12710283/1596489

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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)

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Mojo urk ¶

6 years ago

Solving round_down() problem: 
-----------------------------
Use of <?php floor(pow(10, $precision) * $value) / pow(10, $precision); ?> fails in some cases, e.g. round_down(2.05, 2) gives incorrect 2.04.
Here is a "string" solution (https://stackoverflow.com/a/26491492/1245149) of the problem (a negative precision is not covered):

<?php
function round_down($value, $precision) {        
    $value = (float)$value;
    $precision = (int)$precision;
    if ($precision < 0) { 
        $precision = 0;
    }
    $decPointPosition = strpos($value, '.');
    if ($decPointPosition === false) { 
        return $value;
    }
    return (float)(substr($value, 0, $decPointPosition + $precision + 1));        
} 
?>

Solving round_up() problem:
---------------------------
Use of <?php ceil(pow(10, $precision) * $value) / pow(10, $precision);?> fails in some cases, e.g. round_up(2.22, 2) gives incorrect 2.23 (https://stackoverflow.com/a/8239620/1245149).
Adapting the above round_down() "string" solution I have got this result (a negative precision is not covered):

<?php
function round_up($value, $precision) {        
    $value = (float)$value;
    $precision = (int)$precision;
    if ($precision < 0) { 
        $precision = 0;
    }
    $decPointPosition = strpos($value, '.');
    if ($decPointPosition === false) { 
        return $value;
    }
    $floorValue = (float)(substr($value, 0, $decPointPosition + $precision + 1));
    $followingDecimals = (int)substr($value, $decPointPosition + $precision + 1);
    if ($followingDecimals) {
        $ceilValue = $floorValue + pow(10, -$precision); // does this give always right result?
    }
    else {
        $ceilValue = $floorValue;
    }
    return $ceilValue;                
}
?>

I don't know it is bulletproof, but at least it removes the above mentioned fail. I have done no binary-to-decimal-math-analysis but if `$floorValue + pow(10, 0 - $precision)` works
always as expected then it should be ok.

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serg at kalachev dot ru ¶

10 years ago

Excel-like ROUNDUP function:

public static function round_up($value, $places) 
{
    $mult = pow(10, abs($places)); 
     return $places < 0 ?
    ceil($value / $mult) * $mult :
        ceil($value * $mult) / $mult;
}

echo round_up(12345.23, 1); // 12345.3
echo round_up(12345.23, 0); // 12346 
echo round_up(12345.23, -1); // 12350 
echo round_up(12345.23, -2); // 12400 
echo round_up(12345.23, -3); // 13000 
echo round_up(12345.23, -4); // 20000

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jongbumi at gmail dot com ¶

8 years ago

PHP 5.3, 5.4, 5.5
<?php
$fInfinty = pow(1000, 1000); // float(INF)
$fResult = round(123.456, $fInfinty); // double(123)
?>

PHP 5.6
<?php
$fInfinty = pow(1000, 1000); // float(INF)
$fResult = round(123.456, $fInfinty); // float(0)
?>

PHP 7
<?php
$fInfinty = pow(1000, 1000); // float(INF)
$fResult = round(123.456, $fInfinty); // null
?>

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djcox99 at googlemail dot com ¶

10 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.

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esion99 at gmail dot com ¶

10 years ago

Unexpected result or misunderstanding (php v5.5.9)

<?php

echo round(1.55, 1, PHP_ROUND_HALF_DOWN); // 1.5
echo round(1.551, 1, PHP_ROUND_HALF_DOWN); //1.6

?>

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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;

echo round($a, 2); // 0.75



setlocale(LC_ALL, 'it_IT@euro', 'it_IT', 'it');

$b=3/4;

echo round($b,2); // 0,75

?>

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twan at ecreation dot nl ¶

24 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 .

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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

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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  

function roundUpTo($number, $increments) {

    $increments = 1 / $increments;

    return (ceil($number * $increments) / $increments);

}

?>

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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

function roundTo($number, $to){

    return round($number/$to, 0)* $to;

}



echo roundTo(87.23, 20); //80

echo roundTo(-87.23, 20); //-80

echo roundTo(87.23, .25); //87.25

echo roundTo(.23, .25); //.25

?>

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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
 * 
 */

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dastra ¶

12 years ago

round() will sometimes return E notation when rounding a float when the amount is small enough - see  https://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));

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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

function RoundSigDigs($number, $sigdigs) {

    $multiplier = 1;

    while ($number < 0.1) {

        $number *= 10;

        $multiplier /= 10;

    }

    while ($number >= 1) {

        $number /= 10;

        $multiplier *= 10;

    }

    return round($number, $sigdigs) * $multiplier;

}

?>

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martinr at maarja dot net ¶

16 years ago

Please note that the format of this functions output also depends on your locale settings. For example, if you have set your locale to some country that uses commas to separate decimal places, the output of this function also uses commas instead of dots.

This might be a problem when you are feeding the rounded float number into a database, which requires you to separate decimal places with dots.

See it in action:
<?php
    echo round('3.5558', 2);
    setlocale(constant('LC_ALL'), 'et_EE.UTF-8');
    echo '<br />'. round('3.5558', 2);
?>

The output will be:
3.56
3,56

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Anonymous ¶

8 years ago

Note that PHP 5.3 didn't just introduce $mode, it rewrote the rounding implementation completely to eliminate many kinds of rounding errors common to rounding floating point values.

That's why round() gives you the correct result even when floor/ceil don't.
For example,  floor(0.285 * 100 + 0.5) VS round(0.285*100 + 0.5). First one gives 28, second one gives 29.

More details here: https://wiki.php.net/rfc/rounding

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feha at vision dot to ¶

14 years ago

Here is a short neat function to round minutes (hour) ...

<?php

function minutes_round ($hour = '14:03:32', $minutes = '5', $format = "H:i")
{
    // by Femi Hasani [www.vision.to]
    $seconds = strtotime($hour);
    $rounded = round($seconds / ($minutes * 60)) * ($minutes * 60);
    return date($format, $rounded);
}

?>

You decide to round to nearest minute ...
example will produce : 14:05

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goreyshi at gmail dot com ¶

6 years ago

When you have a deal with money like dollars, you need to display it under this condition:
-format all number with two digit decimal for cents.
-divide 1000 by ,
-round half down for number with more than two decimal

I approach it using round function inside the number_format function:

number_format((float)round( 625.371 ,2, PHP_ROUND_HALF_DOWN),2,'.',',')  // 625.37
number_format((float)round( 625.379 ,2, PHP_ROUND_HALF_DOWN),2,'.',',')  // 625.38
number_format((float)round( 1211.20 ,2, PHP_ROUND_HALF_DOWN),2,'.',',')  // 1,211.20
number_format((float)round( 625 ,2, PHP_ROUND_HALF_DOWN),2,'.',',')      // 625.00

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-2

omnibus at omnibus dot edu dot pl ¶

14 years ago

Beware strange behaviour if number is negative and precision is bigger than the actual number of digits after comma.

round(-0.07, 4);

returns

-0.07000000000000001

So if you validate it against a regular expression requiring the maximum amount of digits after comma, you'll get into trouble.

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-1

Astro ¶

4 years ago

Okay, final version of my function:

function NumberPrecision($n, $precision=0, $is_round=true)
            {
            if ($is_round)
                {
                $r = 5 * pow(10, -($precision+1));
                $n += (($n < 0) ? -$r : $r);
                }
            
            $comma = '.';
            
            $r = 5 * pow(10, -($precision+2));
            $n += (($n > 0) ? -$r : $r);
            $n = number_format($n, $precision+1, $comma, '');
            
            $n .= $comma;
            list($n, $frac) = explode($comma, $n, 2);
            $n = rtrim(rtrim($n, $comma) . $comma . substr($frac, 0, $precision), $comma);
            return ($n);
            }

It can be useful in come cases when built-in function like round() or number_format() returns unexpected results. Works with positive and negative numbers, zero, numbers like 1/12, 0.3, numbers in scientific notation etc.

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-1

terry at scribendi dot com ¶

20 years ago

To round any number to a given number of significant digits, use log10 to find out its magnitude:



<?php round($n, ceil(0 - log10($n)) + $sigdigits); ?>



Or when you have to display a per-unit price which may work out to be less than a few cents/pence/yen you can use:



<?php

// $exp = currency decimal places - 0 for Yen/Won, 2 for most others

$dp = ceil(0 - log10($n)) + $sigdigits;

$display = number_format($amount, ($exp>$dp)?$exp:$dp);

?>



This always displays at least the number of decimal places required by the currency, but more if displaying the unit price with precision requires it - eg: 'English proofreading from $0.0068 per word', 'English beer from $6.80 per pint'.

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-2

Anonymous ¶

15 years ago

This functions return ceil($nb) if the double or float value is bigger than "$nb.5" else it's return floor($nb)



<?php

    function arounds_int($nb) {

     

        if(!is_numeric($nb)) {

            return false;

        }

        

        $sup = round($nb);

        $inf = floor($nb);

        $try = (double) $inf . '.5' ; 

        

        if($nb > $try) {

            return $sup;

        }

        

        return $inf;

    }

?>

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-3

Anonymous ¶

7 years ago

This function has strange. behaviors:

<?php
echo round(0.045, 2);      // 0.05
echo round(0.45, 1);      // 0.5
echo round(1.045-1, 2);    // 0.04 !!!
echo round(1.45-1, 1);      // 0.5

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-1

Hayley Watson ¶

5 years ago

It should just be noted that what is called "precision" on this page is more correctly called accuracy; precision is the total number of significant digits on both sides of the decimal point, while accuracy is the number of digits to the right of the point. It's a common confusion.

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-3

spectrumcat at gmail dot com ¶

10 years ago

In case someone will need a "graceful" rounding (that changes it's precision to get a non 0 value) here's a simple function:

function gracefulRound($val, $min = 2, $max = 4) {
    $result = round($val, $min);
    if ($result == 0 && $min < $max) {
        return gracefulRound($val, ++$min, $max);
    } else {
        return $result;
    }
}

Usage:
$_ = array(0.5, 0.023, 0.008, 0.0007, 0.000079, 0.0000048);
foreach ($_ as $val) {
    echo "{$val}: ".gracefulRound($val)."\n";
}

Output:
0.5: 0.5
0.023: 0.02
0.008: 0.01
0.0007: 0.001
0.000079: 0.0001
0.0000048: 0

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-4

maxteiber at gmail dot com ¶

18 years ago

the result of this function always depends on the underlying C function. There have been a lot of compiler bugs and floating-point precission problems involving this function. Right now the following code:

<?php
echo round(141.075, 2);
?>

returns:

141.07

on my machine.
So never really trust this function when you do critical calculations like accounting stuff!
Instead: use only integers or use string comparisons.

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-3

php at persignum dot com ¶

9 years ago

Because this function is missing round up and round down constants and the top note doesn't really show you how to round up or down to the nearest number, here is an easy way to always round up or always round down to the nearest number.

int is the number you want to round

n is the nearest number you want rounded to.

Round up to the nearest number

function round_up($int, $n) {
    return ceil($int / $n) * $n;
}

And to round down to the nearest number

function round_down(int, $n) {
    return floor($int / $n) * $n;
}

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