Round to one decimal javascript

Mastering Rounding to One Decimal Place in JavaScript: Methods and Examples

Learn how to round numbers to one decimal place in JavaScript with built-in functions and custom methods. Avoid errors caused by floating point math and improve your programming skills. Read now!

Rounding numbers is a very common task in JavaScript programming. One of the most common use cases is rounding numbers to one decimal place. There are different methods available for doing this, each with its own advantages and disadvantages. In this blog post, we will explore different ways to round numbers to one decimal place in JavaScript, including built-in functions and custom methods.

Adding the Smallest Possible Float Value

To round a number to one decimal place in JavaScript, add the smallest possible float value to the number before rounding. This method can help avoid errors caused by floating point math. Here is an example code:

let num = 5.6789; num = (Math.round(num * 10 + Number.EPSILON) / 10).toFixed(1); console.log(num); // Output: 5.7 

In this code, we first multiply the number by 10 and add the smallest possible float value to it. We then use the Math.round() function to round the result to the nearest integer. Finally, we divide the result by 10 and use the toFixed() function to round it to one decimal place.

Using Math.round() Function

Another way to round a number to one decimal place is to use the Math.round() function to round the result of multiplying the number by 10 and then dividing it by 10. This method is straightforward and easy to use. Here is an example code:

let num = 5.6789; num = Math.round(num * 10) / 10; console.log(num.toFixed(1)); // Output: 5.7 

In this code, we first multiply the number by 10 and then use the Math.round() function to round the result to the nearest integer. Finally, we divide the result by 10 and use the toFixed() function to round it to one decimal place.

Using toFixed() Method

The toFixed() method can be used to round a number to one decimal place in JavaScript. This method returns a string representing the number in fixed-point notation with the specified number of decimal places. Here is an example code:

let num = 5.6789; num = num.toFixed(1); console.log(num); // Output: 5.7 

In this code, we use the toFixed() function to round the number to one decimal place.

Multiplying and Dividing by 10 with Math.ceil() Function

Another way to round a number to one decimal place in JavaScript is to multiply the number by 10, then round up to the nearest integer using Math.ceil(), and finally divide the result by 10. This method can help avoid errors caused by floating point math. Here is an example code:

let num = 5.6789; num = Math.ceil(num * 10) / 10; console.log(num.toFixed(1)); // Output: 5.7 

In this code, we first multiply the number by 10 and then use the Math.ceil() function to round up to the nearest integer. Finally, we divide the result by 10 and use the toFixed() function to round it to one decimal place.

Rounding to a Certain Number of Decimal Places and Stripping Extra Zeros

There are several methods available to round a number to a certain number of decimal places and strip extra zeros. One way is to use the parseFloat() function to strip extra zeros when rounding to a certain number of decimal places. Here is an example code:

let num = 5.6789; num = parseFloat(num.toFixed(2)); console.log(num); // Output: 5.68 

In this code, we first use the toFixed() function to round the number to two decimal places. We then use the parseFloat() function to strip extra zeros and convert the result back to a number.

Other examples of simple code for rounding numbers to one decimal place in JavaScript

In Javascript , in particular, js round up decimal code sample

Math.round(3.14159) // 3 Math.round(3.5) // 4 Math.floor(3.8) // 3 Math.ceil(3.2) // 4 

In Javascript , for instance, math.round js 1 decimal code sample

var number = 12.3456789; var rounded = Math.round( number * 10 ) / 10; // rounded is 12.3

In Javascript , for instance, javascript round decimal code example

Number((6.688689).toFixed(2)); // 6.69

In Javascript , for instance, javascript round to 1 decimal code example

var subTotal="12.1345";// can also be int, float, string var subTotalFormatted=parseFloat(subTotal).toFixed(2); //"12.13"

In Javascript , for instance, round decimal js code example

In Javascript case in point, round number 2 decimals javascript code sample

Math.round((num + Number.EPSILON) * 100) / 100

In Javascript as proof, round to decimal javascript code sample

function round(value, precision) < var multiplier = Math.pow(10, precision || 0); return Math.round(value * multiplier) / multiplier; >

In Javascript , for example, javascript round to 7 decimal places code example

In Javascript , round 2 decimales js code sample

var numb = 80.124124124; numb = numb.toFixed(2);// numb = 80.12

Conclusion

Rounding numbers to one decimal place is a common task in JavaScript programming. There are several methods available for doing this, each with its own advantages and disadvantages. The best method to use depends on the specific needs of the project and the desired level of precision. By understanding these methods, JavaScript developers can be more effective in their work and avoid errors caused by floating point math.

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How can I round a number to 1 decimal place in JavaScript?

In this tutorial, we will learn to round a number to a one decimal place in JavaScript. There are various needs to round the float numbers and show particular digits after the decimal point.

In our case, we need to show only the digit after the decimal point. However, we will create a customizable manual function that can round off the number and show the particular number of digits after the decimal point at the end of this tutorial.

This example lets users understand the fundamental need to round a number to a single decimal digit. Suppose the scenario where you are developing the application for the online store, and you need to show the price of every product, but in the database, you have stored the price till five digits after the decimal point. After fetching the price of products from the database, you need to show till one decimal digit. In this case, you must find a way to solve your problem.

Furthermore, we have different methods to achieve our goal in this tutorial.

Using the toFixed() Method

In this approach, we will round a number to 1 decimal place using the toFixed() method. It takes a single parameter; the number of digits you want to keep after the decimal point. Also, the toFixed() method “returns the string output” even if you add a number input. We need to convert the string output to float.

Syntax

Users can follow the below syntax to use the toFixed() method.

number.toFixed(decimal_digits);

Parameters

• decimal_digits − This parameter takes the number input which represent the number of digits you want to keep after decimal point. In our case, we will take 1 as this parameter.

Example

The below example demonstrates how to use the toFixed() method to round numbers to 1 decimal place. As discussed above, the toFixed() method returns a string so that we will convert the returned string value to the float again.

   
Round a number to 1 decimal place in JavaScript
 
After rounding the 103.72456 to 1 decimal place, output is
      

In the above output, users can see that type of output after rounding the number to 1 decimal place using the toFixed() method is a string. After that, we have converted output to float using the parseFloat() function.

Using the Math.round() function

We will use the Math.round() function from the JavaScript math library in this approach. The Math.round() function round off the number to its nearest number, but we will apply some precious logic to round of number to a single digit only.

We can multiply the number by 10 and apply the round() function. After that, we can divide the rounded number by 10 again, so we can achieve our goal.

Users can understand the above approach using this example. For example, we want to round a number 10.34532 to 1 decimal digit. Let’s multiply the number by 10, and it turns to 103.4532. Now, if we apply the round function, we get result 103 only. Next, divide the number by 10, the number turns to 10.3, and we get the correct result.

Syntax

let result = Math.round(number*10)/10;

Example

In the below example, we have created a rounding function so that users can customize it according to their needs. Our function takes 2 parameters, one is the number you want to round off, and another is the number of digits you want to keep after decimal points.

   
Round a number to 1 decimal place in JavaScript
 
Result after rounding the 81.43426 to 1 decimal place using the Math.Round() method −
    

In the above example, we have passed the 1 as a value of the decimal_digit parameter. So, we will get 101 = 10, and Math.round() function rounds number to 1 decimal place.

If users want to round numbers to n decimal place, they will pass n as decimal_digit value, and as a power of 10, they get 10n and Math.round() function round off a number to n decimal place.

Conclusion

In this tutorial, we used two approaches to round numbers to a single decimal place. The first approach is not so good as it returns the string, and you need to convert it into float again. The second approach is beneficial as it is customizable even though it will work round off numbers to n decimal places.

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Math.round()

The Math.round() static method returns the value of a number rounded to the nearest integer.

Try it

Syntax

Parameters

Return value

The value of x rounded to the nearest integer.

Description

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. If the fractional portion is exactly 0.5, the argument is rounded to the next integer in the direction of +∞.

Note: This differs from many languages’ round() functions, which often round half-increments away from zero, giving a different result in the case of negative numbers with a fractional part of exactly 0.5.

Because round() is a static method of Math , you always use it as Math.round() , rather than as a method of a Math object you created ( Math has no constructor).

Examples

Using round

.round(-Infinity); // -Infinity Math.round(-20.51); // -21 Math.round(-20.5); // -20 Math.round(-0.1); // -0 Math.round(0); // 0 Math.round(20.49); // 20 Math.round(20.5); // 21 Math.round(42); // 42 Math.round(Infinity); // Infinity 

Specifications

Browser compatibility

BCD tables only load in the browser

See also

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This page was last modified on Feb 21, 2023 by MDN contributors.

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