Log Calculator
Find logarithms to any base, including ln, log10 and log2.
What a logarithm answers
A logarithm asks: to what power must the base be raised to get this number? Since 103 = 1,000, the log base 10 of 1,000 is 3. Since 23 = 8, the log base 2 of 8 is 3.
Common bases
- Base 10 (log): used for scales such as pH and decibels.
- Base e (ln, the natural log): used in growth and calculus.
- Base 2: used in computing and information.
Change of base
For any base, logb(x) = ln(x) ÷ ln(b). The number must be positive, and the base must be positive and not equal to 1.
Frequently asked questions
Can I take the log of zero or a negative number?
Not in real numbers. The logarithm is only defined for positive numbers.
What is e?
Euler's number, about 2.71828. The natural log uses e as its base.
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