javascript float to int round down

How do I convert a float number to a whole number in JavaScript?

stackoverflow.com › questions › 596467 › how-do-i-convert-a-float-number-to-a-whole-number-in-javascript

var intvalue = Math.floor( floatvalue );
var intvalue = Math.ceil( floatvalue ); 
var intvalue = Math.round( floatvalue );

// `Math.trunc` was added in ECMAScript 6
var intvalue = Math.trunc( floatvalue );

Math object reference

Examples

Positive

// value=x        //  x=5          5<x<5.5      5.5<=x<6  

Math.floor(value) //  5            5            5
Math.ceil(value)  //  5            6            6
Math.round(value) //  5            5            6
Math.trunc(value) //  5            5            5
parseInt(value)   //  5            5            5
~~value           //  5            5            5
value | 0         //  5            5            5
value >> 0        //  5            5            5
value >>> 0       //  5            5            5
value - value % 1 //  5            5            5

Negative

// value=x        // x=-5         -5>x>=-5.5   -5.5>x>-6

Math.floor(value) // -5           -6           -6
Math.ceil(value)  // -5           -5           -5
Math.round(value) // -5           -5           -6
Math.trunc(value) // -5           -5           -5
parseInt(value)   // -5           -5           -5
value | 0         // -5           -5           -5
~~value           // -5           -5           -5
value >> 0        // -5           -5           -5
value >>> 0       // 4294967291   4294967291   4294967291
value - value % 1 // -5           -5           -5

Positive - Larger numbers

// x = Number.MAX_SAFE_INTEGER/10 // =900719925474099.1

// value=x            x=900719925474099    x=900719925474099.4  x=900719925474099.5
           
Math.floor(value) //  900719925474099      900719925474099      900719925474099
Math.ceil(value)  //  900719925474099      900719925474100      900719925474100
Math.round(value) //  900719925474099      900719925474099      900719925474100
Math.trunc(value) //  900719925474099      900719925474099      900719925474099
parseInt(value)   //  900719925474099      900719925474099      900719925474099
value | 0         //  858993459            858993459            858993459
~~value           //  858993459            858993459            858993459
value >> 0        //  858993459            858993459            858993459
value >>> 0       //  858993459            858993459            858993459
value - value % 1 //  900719925474099      900719925474099      900719925474099

Negative - Larger numbers

// x = Number.MAX_SAFE_INTEGER/10 * -1 // -900719925474099.1

// value = x      // x=-900719925474099   x=-900719925474099.5 x=-900719925474099.6

Math.floor(value) // -900719925474099     -900719925474100     -900719925474100
Math.ceil(value)  // -900719925474099     -900719925474099     -900719925474099
Math.round(value) // -900719925474099     -900719925474099     -900719925474100
Math.trunc(value) // -900719925474099     -900719925474099     -900719925474099
parseInt(value)   // -900719925474099     -900719925474099     -900719925474099
value | 0         // -858993459           -858993459           -858993459
~~value           // -858993459           -858993459           -858993459
value >> 0        // -858993459           -858993459           -858993459
value >>> 0       //  3435973837           3435973837           3435973837
value - value % 1 // -900719925474099     -900719925474099     -900719925474099

Answer from moonshadow on Stack Overflow

MDN Web Docs

developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Math › round

Math.round() - JavaScript | MDN

If the fractional portion of the argument is greater than 0.5, the argument is rounded to the integer with the next higher absolute value. If it is less than 0.5, the argument is rounded to the integer with the lower absolute value.

W3Schools

w3schools.com › jsref › jsref_round.asp

JavaScript Math round() Method

The Math.round() method rounds a number to the nearest integer. 2.49 will be rounded down (2), and 2.5 will be rounded up (3). The Math.abs() Method The Math.ceil() Method The Math.floor() Method The Math.round() Method The Math.fround() Method ...

Stack Overflow

stackoverflow.com › questions › 596467 › how-do-i-convert-a-float-number-to-a-whole-number-in-javascript

syntax - How do I convert a float number to a whole number in JavaScript? - Stack Overflow

Top answer

1 of 16

2261

var intvalue = Math.floor( floatvalue );
var intvalue = Math.ceil( floatvalue ); 
var intvalue = Math.round( floatvalue );

// `Math.trunc` was added in ECMAScript 6
var intvalue = Math.trunc( floatvalue );

Math object reference

Examples

Positive

// value=x        //  x=5          5<x<5.5      5.5<=x<6  

Math.floor(value) //  5            5            5
Math.ceil(value)  //  5            6            6
Math.round(value) //  5            5            6
Math.trunc(value) //  5            5            5
parseInt(value)   //  5            5            5
~~value           //  5            5            5
value | 0         //  5            5            5
value >> 0        //  5            5            5
value >>> 0       //  5            5            5
value - value % 1 //  5            5            5

Negative

// value=x        // x=-5         -5>x>=-5.5   -5.5>x>-6

Math.floor(value) // -5           -6           -6
Math.ceil(value)  // -5           -5           -5
Math.round(value) // -5           -5           -6
Math.trunc(value) // -5           -5           -5
parseInt(value)   // -5           -5           -5
value | 0         // -5           -5           -5
~~value           // -5           -5           -5
value >> 0        // -5           -5           -5
value >>> 0       // 4294967291   4294967291   4294967291
value - value % 1 // -5           -5           -5

Positive - Larger numbers

// x = Number.MAX_SAFE_INTEGER/10 // =900719925474099.1

// value=x            x=900719925474099    x=900719925474099.4  x=900719925474099.5
           
Math.floor(value) //  900719925474099      900719925474099      900719925474099
Math.ceil(value)  //  900719925474099      900719925474100      900719925474100
Math.round(value) //  900719925474099      900719925474099      900719925474100
Math.trunc(value) //  900719925474099      900719925474099      900719925474099
parseInt(value)   //  900719925474099      900719925474099      900719925474099
value | 0         //  858993459            858993459            858993459
~~value           //  858993459            858993459            858993459
value >> 0        //  858993459            858993459            858993459
value >>> 0       //  858993459            858993459            858993459
value - value % 1 //  900719925474099      900719925474099      900719925474099

Negative - Larger numbers

// x = Number.MAX_SAFE_INTEGER/10 * -1 // -900719925474099.1

// value = x      // x=-900719925474099   x=-900719925474099.5 x=-900719925474099.6

Math.floor(value) // -900719925474099     -900719925474100     -900719925474100
Math.ceil(value)  // -900719925474099     -900719925474099     -900719925474099
Math.round(value) // -900719925474099     -900719925474099     -900719925474100
Math.trunc(value) // -900719925474099     -900719925474099     -900719925474099
parseInt(value)   // -900719925474099     -900719925474099     -900719925474099
value | 0         // -858993459           -858993459           -858993459
~~value           // -858993459           -858993459           -858993459
value >> 0        // -858993459           -858993459           -858993459
value >>> 0       //  3435973837           3435973837           3435973837
value - value % 1 // -900719925474099     -900719925474099     -900719925474099

2 of 16

348

Bitwise OR operator

A bitwise or operator can be used to truncate floating point figures and it works for positives as well as negatives:

function float2int (value) {
    return value | 0;
}

Results

float2int(3.1) == 3
float2int(-3.1) == -3
float2int(3.9) == 3
float2int(-3.9) == -3

Performance comparison?

I've created a JSPerf test that compares performance between:

Math.floor(val)
val | 0 ^{bitwise OR}
~~val ^{bitwise NOT}
parseInt(val)

that only works with positive numbers. In this case you're safe to use bitwise operations well as Math.floor function.

But if you need your code to work with positives as well as negatives, then a bitwise operation is the fastest (OR being the preferred one). This other JSPerf test compares the same where it's pretty obvious that because of the additional sign checking Math is now the slowest of the four.

Note

As stated in comments, BITWISE operators operate on signed 32bit integers, therefore large numbers will be converted, example:

1234567890  | 0 => 1234567890
12345678901 | 0 => -539222987

Stack Overflow

stackoverflow.com › questions › 1435975 › how-can-i-round-down-a-number-in-javascript

math - How can I round down a number in Javascript? - Stack Overflow

Top answer

1 of 12

493

Using Math.floor() is one way of doing this.

More information: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/floor

2 of 12

Round towards negative infinity - Math.floor()

+3.5 => +3.0
-3.5 => -4.0

Round towards zero can be done using Math.trunc(). Older browsers do not support this function. If you need to support these, you can use Math.ceil() for negative numbers and Math.floor() for positive numbers.

+3.5 => +3.0 using Math.floor()
-3.5 => -3.0 using Math.ceil()

pawelgrzybek

pawelgrzybek.com › rounding-and-truncating-numbers-in-javascript

Rounding and truncating numbers in JavaScript | pawelgrzybek.com

Luckily there is a way to use this without ES6 support (thanks to Johny who suggested this solution in comments below). We can use bitwise operators to accomplish this task. Unfortunately there are some restriction as well. All bitwise operations work on signed 32-bit integers. Using them converts a float to an integer.

Stack Abuse

stackabuse.com › how-to-round-doubles-or-floats-in-javascript

How to Round Doubles/Floats in JavaScript

February 22, 2022 - In this tutorial - learn how to round decimal numbers (floats/doubles) in JavaScript to whole integers - up, down or nearest.

Code Highlights

code-hl.com › home › javascript › tutorials

5 Easy Ways to Convert JavaScript Float to Int | Code Highlights

June 4, 2024 - In this tutorial, we explored five simple methods to convert a JavaScript float to an int: Math.floor(): Rounds down to the nearest integer.

JavaScript.info

javascript.info › tutorial › the javascript language › data types

Numbers

Also in many countries, the currency symbol goes after the amount, so we have "19€" and would like to extract a numeric value out of that. That’s what parseInt and parseFloat are for. They “read” a number from a string until they can’t. In case of an error, the gathered number is returned. The function parseInt returns an integer, whilst parseFloat will return a floating-point number:

TutorialsPoint

tutorialspoint.com › How-can-I-round-down-a-number-in-JavaScript

How can I round down a number in JavaScript?

In the above output, users can see that after rounding down, 10234.2433341 becomes 10234, which is the nearest small integer to 10234.2433341. If we perform the Bitwise operator on any float number, it removes the decimal part of the number.

Find elsewhere

Google Bing Mojeek

Byby

byby.dev › js-float-to-int

How to convert float to integer in JavaScript

Using Math.floor(): This function rounds down to the nearest integer. When you apply it to a positive float, it will return the largest integer less than or equal to the float.

Linux Hint

linuxhint.com › different-methods-to-round-float-numbers-in-javascript

Different Methods to Round Float Numbers in JavaScript?

Linux Hint LLC, [email protected] 1210 Kelly Park Circle, Morgan Hill, CA 95037 Privacy Policy and Terms of Use

Delft Stack

delftstack.com › home › howto › javascript › javascript float to int

How to Convert a Float Number to Int in JavaScript | Delft Stack

February 2, 2024 - Else, if the value after the decimal is lesser than 5, it is rounded to the lower integer. Hence, based on the value post the decimal point, Math.round() function can behave similar to Math.floor() or Math.ceil() functions.

W3Schools

w3schools.com › jsref › jsref_floor.asp

JavaScript Math floor() Method

The Math.floor() method rounds a number DOWN to the nearest integer. The Math.abs() Method The Math.ceil() Method The Math.floor() Method The Math.round() Method The Math.fround() Method The Math.f16round() Method The Math.trunc() Method ...

SheCodes

shecodes.io › athena › 12443-how-to-round-up-a-float-in-javascript

[JavaScript] - How to round up a float in JavaScript - | SheCodes

Learn how to use the Math.ceil() function to round up a float in JavaScript and log it to the console.

Stack Overflow

stackoverflow.com › questions › 11187367 › round-a-float-up-to-the-next-integer-in-javascript

floating point - Round a float up to the next integer in javascript - Stack Overflow

Top answer

1 of 4

148

Use the Math.ceil^[MDN] function

var n = 4.3;
alert(Math.ceil(n)); //alerts 5

2 of 4

Use ceil

var n = 4.3;
n = Math.ceil(n);// n is 5

Kodeclik

kodeclik.com › javascript-round-down

How to round down a number in Javascript

October 24, 2025 - Note that Math.floor() rounds down to the nearest integer, regardless of whether the input is an integer or a floating-point number.

Sonasa

sonasa.cv › c5tan › javascript-float-to-int-round-down

javascript float to int round down

Math.round () is a built-in method in JavaScript that cuts off the floating-point value and returns an integer. (A1) Multiply the given number by an offset first. The only difference is with negative numbers, where floor() will round -4.5 down to -5 whereas typecasting would return -4.

Stack Overflow

stackoverflow.com › questions › 9453421 › how-to-round-float-numbers-in-javascript

rounding - How to round float numbers in javascript? - Stack Overflow

Top answer

1 of 16

709

Number((6.688689).toFixed(1)); // 6.7

2 of 16

213

var number = 6.688689;
var roundedNumber = Math.round(number * 10) / 10;

CoreUI

coreui.io › answers › how-to-round-a-number-in-javascript

How to round a number in JavaScript · CoreUI

September 26, 2025 - Use Math.round() to round numbers to the nearest integer or combine with multiplication for decimal precision in JavaScript.

Stack Overflow

stackoverflow.com › questions › 34077449 › fastest-way-to-cast-a-float-to-an-int-in-javascript

performance - Fastest way to cast a float to an int in javascript? - Stack Overflow

Top answer

1 of 7

Great Question! I actually had to deal with this the other day! It may seem like a goto to just write parseInt but wait! we can be fancier.

So we can use bit operators for quite a few things and this seems like a great situation! Let's say I have the number from your question, 12.345, I can use the bit operator '~' which inverts all the bits in your number and in the process converts the number to an int! Gotta love JS.

So now we have the inverted bit representation of our number then if we '~' it again we get ........drum roll......... our number without the decimals! Unfortunately, it doesn't do rounding.

var a = 12.345;
var b = ~~a; //boom!

We can use Math.round() for that. But there you go! You can try it on JSperf to see the slight speed up you get! Hope that helps!

2 of 7

this is a good example i think

var intvalue = Math.floor( floatvalue );
var intvalue = Math.ceil( floatvalue ); 
var intvalue = Math.round( floatvalue );