Math.log10()

Math.log10(x)

Returns: number · Added in vES1 · Updated March 13, 2026 · Math

math logarithm base-10 numbers scientific data-science

Math.log10() returns the base-10 logarithm of a number. It’s the go-to function when you need to work with decimal (base-10) systems, making it indispensable for calculating magnitude, digit counts, pH calculations, decibel conversions, and any application involving powers of 10.

Syntax

Math.log10(x)

Parameters

Parameter	Type	Description
`x`	`number`	A number greater than or equal to zero

Return Value

Input	Return Value
`x > 0`	The base-10 logarithm of `x`
`x = 1`	`0` (since 10⁰ = 1)
`x = 10`	`1` (since 10¹ = 10)
`x = 100`	`2` (since 10² = 100)
`x = 0`	`-Infinity`
`x < 0`	`NaN`
`x = NaN`	`NaN`

Examples

Calculating the magnitude of a number

// Determine how many powers of 10: the "order of magnitude"
console.log(Math.log10(1));
// 0

console.log(Math.log10(50));
// 1.6989700043360187

console.log(Math.log10(1000));
// 3

console.log(Math.log10(0.001));
// -3

Counting digits in a number

// Useful for formatting, validation, and display
function countDigits(n) {
  return Math.floor(Math.log10(n)) + 1;
}

console.log(countDigits(12345));
// 5

console.log(countDigits(999));
// 3

console.log(countDigits(1));
// 1

Handling edge cases

// Zero returns -Infinity
console.log(Math.log10(0));
// -Infinity

// Negative numbers return NaN (no real logarithm exists)
console.log(Math.log10(-5));
// NaN

// NaN propagates
console.log(Math.log10(NaN));
// NaN

// Infinity returns Infinity
console.log(Math.log10(Infinity));
// Infinity

Comparison: Math.log10() vs Math.log()

While both functions calculate logarithms, they differ in their base:

Math.log(x) — natural logarithm (base e ≈ 2.718)
Math.log10(x) — common logarithm (base 10)

// Math.log10 uses base 10
console.log(Math.log10(100));
// 2 (because 10² = 100)

// Math.log uses base e
console.log(Math.log(100));
// 4.605170185988092 (because e^4.605... = 100)

// You can derive Math.log10 using Math.log and Math.LN10
console.log(Math.log(100) / Math.LN10);
// 2 (same as Math.log10(100))

// Math.LN10 is a constant: Math.log(10) ≈ 2.302585
console.log(Math.LN10);
// 2.302585093

Common Use Cases

Data science and scaling

// Normalize values using log10 to handle exponential data
function normalizeLogScale(values) {
  const max = Math.max(...values);
  return values.map(v => Math.log10(v) / Math.log10(max));
}

console.log(normalizeLogScale([1, 10, 100, 1000]));
// [0, 0.333..., 0.666..., 1]

Scientific notation conversion

// Extract the exponent from scientific notation
function getScientificExponent(n) {
  return Math.floor(Math.log10(Math.abs(n)));
}

console.log(getScientificExponent(3.14e5));
// 5

console.log(getScientificExponent(0.00042));
// -4

Performance Note

Math.log10() is a native JavaScript built-in, optimized in modern engines. For bulk computations in tight loops, the performance is generally adequate. If you need to convert many numbers and know the base is fixed, pre-computing 1 / Math.LN10 can occasionally save a division, but the difference is negligible in most applications.