# Round Off In Javascript (Up, Down, To Decimal Places)

Welcome to a short tutorial on how to round off numbers in Javascript. So you have a project that needs to round off a number?

1. To round off a number in Javascript – `Math.round(12.34);`
2. Round up to the nearest whole number – `Math.ceil(1.1);`
3. Round down to the nearest whole number – `Math.floor(2.3);`
4. Drop the decimal places without rounding off – `Math.trunc(3.45);`
5. Round off to 2 decimal places – `Math.round(12.345 * 100) / 100;`

That covers the basics, but let us walk through more examples – Read on!

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## ROUNDING OFF IN JAVASCRIPT

All right, let us now go into the examples of rounding off numbers in Javascript.

### 1) ROUND, CEILING, FLOOR, TRUNCATE

1-round.html
``````// (A) NUMBERS
var numA = 11.4;
var numB = 12.5;

// (B) ROUND OFF
// < 0.5 - ROUND DOWN
// >= 0.5 - ROUND UP
console.log(Math.round(numA)); // 11
console.log(Math.round(numB)); // 13

// (C) CEILING - ALWAYS ROUND UP
console.log(Math.ceil(numA)); // 12
console.log(Math.ceil(numB)); // 13

// (D) FLOOR - ALWAYS ROUND DOWN
console.log(Math.floor(numA)); // 11
console.log(Math.floor(numB)); // 12

// (E) TRUNCATE - NO ROUND OFF, JUST DROP DECIMAL PLACES
console.log(Math.trunc(numA)); // 11
console.log(Math.trunc(numB)); // 12``````

As in the introduction, there are 4 native Javascript Math functions to round off numbers:

1. `Math.round()` rounds off to the nearest whole number. That is, decimals with less than 0.5 will be rounded down, rounded up if more than or equals to 0.5.
2. `Math.ceil()` will always round up to the nearest whole number.
3. `Math.floor()` will always round down to the nearest whole number.
4. `Math.trunc()` does not do any rounding, simply drops the decimal places.

### 2) ROUNDING TO DECIMAL PLACES

2-places.html
``````// (A) A BETTER ROUND OFF
//   NUM : NUMBER TO BE ROUNDED
//   PLACES : NUMBER OF DECIMAL PLACES
//   MODE : NONE - ROUND, 0 - FLOOR, 1 - CEILING
function rounder (num, places, mode) {
// (A1) MULTIPLIER
var mult = parseInt("1" + "0".repeat(places));
num = num * mult;

// (A2) ROUND OFF
if (mode === 1) { num = Math.ceil(num); }
else if (mode === 0) { num = Math.floor(num); }
else { num = Math.round(num); }

// (A3) RETURN RESULTS
return num / mult;
}

// (B) TEST
var num = 1.2374;
// 2 DECIMALS ROUND - 1.24
console.log(rounder(num, 2));
// 3 DECIMALS FLOOR - 1.237
console.log(rounder(num, 3, 0));
// 3 DECIMALS CEILING - 1.238
console.log(rounder(num, 3, 1));``````

So as you can see, all the native round-off functions will only round to whole numbers. To do a “round off to 2 decimal places”, we need to multiply the number by 100, round off, then divide by 100… That is a little inconvenient, so the smarter way is to create an “improved roundoff” function.

• (A1) Multiply the given number by an offset first. I.E. The offset will be 10 if 1 decimal point, 100 if 2 decimal points, 1000 if 3 decimal points, and so on.
• (A2) Use the `round() ceil() floor()` functions as usual.
• (A3) Finally, “revert” the number by dividing it with the offset.

## EXTRAS

That’s all for this tutorial, and here is a small section on some extras and links that may be useful to you.

### SUMMARY

 Function Description Link `Math.round(NUMBER)` Rounds to the nearest whole number. Click Here `Math.ceil(NUMBER)` Round up to the next whole number. Click Here `Math.floor(NUMBER)` Round down to the last whole number. Click Here `Math.trunc(NUMBER)` Remove decimal places. Click Here

## THE END

Thank you for reading, and we have come to the end of this guide. I hope that it has helped you with your project, and if you want to share anything with this guide, please feel free to comment below. Good luck and happy coding!