Add float numbers using JavaScript

Last Updated : 24 Aug, 2026

Given two or more floating-point numbers, the task is to calculate their sum and display the result in the desired format using JavaScript.

JavaScript uses the IEEE 754 floating-point format, so some decimal calculations may produce results such as 4.699999999999999 instead of 4.7. Formatting methods can be used when a specific number of decimal places is required.

There are the following approaches to add and format float numbers in JavaScript:

Approach 1: Using parseFloat() and toFixed()

The parseFloat() method converts a string into a floating-point number, while the toFixed() method formats the result to a specified number of decimal places.

  • Convert the input values using parseFloat().
  • Add the floating-point numbers.
  • Use toFixed() to format the result.
  • toFixed(2) displays exactly two digits after the decimal point.
JavaScript 
const num1 = parseFloat("2.3");
const num2 = parseFloat("2.4");

const sum = num1 + num2;

console.log("Without formatting:", sum);
console.log("With formatting:", sum.toFixed(2));

Output
Without formatting: 4.699999999999999
With formatting: 4.70

Syntax:

const sum = parseFloat(value1) + parseFloat(value2);
const result = sum.toFixed(2);

Note: toFixed() returns a string, not a number.

Approach 2: Using parseFloat() and Math.round()

The Math.round() method can be used to round the result to a specified number of decimal places.

To round a number to two decimal places:

  • Multiply the result by 100.
  • Apply Math.round().
  • Divide the result by 100.
JavaScript 
const num1 = parseFloat("2.3");
const num2 = parseFloat("2.4");

const sum = num1 + num2;

console.log("Without formatting:", sum);

const roundedSum = Math.round(sum * 100) / 100;

console.log("With rounding:", roundedSum);

Output
Without formatting: 4.699999999999999
With rounding: 4.7

Syntax:

const sum = parseFloat(value1) + parseFloat(value2);
const result = Math.round(sum * 100) / 100;

Note: Unlike toFixed(), Math.round() returns a number and does not preserve trailing zeros. For example, 4.70 becomes 4.7.

Approach 3: Using Number() and Intl.NumberFormat

The Number() function can convert numeric strings into numbers, while Intl.NumberFormat can format the result according to the required number of decimal places.

  • Convert the input values using Number().
  • Add the numbers.
  • Use Intl.NumberFormat to format the result.
  • Set minimumFractionDigits and maximumFractionDigits to control decimal places.
JavaScript 
const num1 = Number("2.3");
const num2 = Number("2.4");

const sum = num1 + num2;

console.log("Without formatting:", sum);

const formattedSum = new Intl.NumberFormat("en-US", {
    minimumFractionDigits: 2,
    maximumFractionDigits: 2
}).format(sum);

console.log("With formatting:", formattedSum);

Output
Without formatting: 4.699999999999999
With formatting: 4.70

Syntax:

const sum = Number(value1) + Number(value2);

const result = new Intl.NumberFormat("en-US", {
    minimumFractionDigits: 2,
    maximumFractionDigits: 2
}).format(sum);

Note: Intl.NumberFormat is useful when the result needs to be displayed in a specific number format, such as currency, percentages, or locale-specific formatting.

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