math.log10

Calculate the base-10 logarithm of a number.

Python 3.13
math.log10(x)

x: A positive number.
int | float

Return value

A float; raises ValueError for zero and negative numbers.

Examples

Base-10 logarithm

Python 3.13
import math
print(math.log10(100))
2.0

Number of digits in a number

Python 3.13
import math
number = 12345
print(int(math.log10(number)) + 1)
5

Details

It is more accurate than math.log(x, 10): math.log10(1000) gives exactly 3.0, and math.log(1000, 10) gives 2.9999999999999996. The integer part of the base-10 logarithm of a positive integer is one less than its number of digits, but only while float precision is enough, up to about 15 digits; len(str(n)) is reliable for any number.