How do you round a number to one decimal place in JavaScript?

General Discussions
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1

I want to round a number so that it shows only one digit after the decimal point, properly rounded.

I tried multiplying by 10, using Math.round(), and then dividing by 10, but sometimes it still shows two decimals. What’s the best way to handle javascript round to 1 decimal correctly?

2

Yeah, your approach is right, multiply by 10, round, then divide by 10:

function roundToOneDecimal(num) {
  return Math.round(num * 10) / 10;
}

This gives you a number rounded to one decimal place.

Just remember the result is a number, so when you print it, JavaScript might show more decimals because of how it handles floating-point numbers.

3

I agree you approach is right @kusha.kpr, however, if you want a string with exactly one decimal place (even if it’s zero), try toFixed(1):

const roundedStr = num.toFixed(1);

This returns a string like “2.30” or “1.00”. It rounds properly and always shows one decimal digit. If you want it back as a number, wrap it with parseFloat().

4

Just an opinion here , sometimes, because of floating-point precision, you might see weird things like 1.999999 rounding oddly.

Using Math.round(num * 10) / 10 is usually fine, but for really accurate decimal math, consider libraries like Decimal.js.

For everyday use, toFixed(1) is your best friend.