How to round up to the nearest N in JavaScript

In JavaScript, rounding a number to the nearest multiple of N requires dividing by N, rounding the result, then multiplying back by N.

Consider this example:

const num = 76;

When rounding to different factors:

• Round to nearest 10: 76 becomes 80

• Round to nearest 100: 76 becomes 100

• Round to nearest 1000: 76 becomes 0

We need a JavaScript function that takes a number and a rounding factor, returning the rounded result.

Syntax

const roundOffTo = (num, factor = 1) => {
    const quotient = num / factor;
    const res = Math.round(quotient) * factor;
    return res;
};

Example

const num = 76;

const roundOffTo = (num, factor = 1) => {
    const quotient = num / factor;
    const res = Math.round(quotient) * factor;
    return res;
};

console.log(roundOffTo(num, 10));
console.log(roundOffTo(num, 100));
console.log(roundOffTo(num, 1000));

Output

80
100
0

How It Works

The algorithm works in three steps:

1. Divide: num / factor converts the number to units of the factor
2. Round: Math.round() rounds to the nearest integer
3. Scale back: Multiply by the factor to get the final result

More Examples

// Round to nearest 5
console.log(roundOffTo(23, 5));  // 25
console.log(roundOffTo(22, 5));  // 20

// Round to nearest 50
console.log(roundOffTo(123, 50)); // 100
console.log(roundOffTo(175, 50)); // 200

25
20
100
200

Conclusion

To round to the nearest N, divide by N, apply Math.round(), then multiply by N. This technique works for any positive rounding factor.