Free online logarithm calculator. Calculate natural logs (ln), common logs (log10), binary logs (log2), and logs with custom bases instantly. No installation required.
Calculate logarithms with any base. Supports common (log₁₀), natural (ln), and binary (log₂) logarithms instantly. This free online tool allows you to calculate logarithms quickly and accurately. No sign-up or installation required.
The Complete Guide to Logarithms
Logarithms are the mathematical inverse of exponents. While an exponent tells you how many times to multiply a base by itself, a logarithm tells you what exponent is needed to achieve a specific number.
Core Logarithm Types
1. Common Logarithm (log₁₀)
The common logarithm uses a base of 10. It is widely used in science and engineering. For example, the Richter scale for earthquakes and the decibel scale for sound are both base-10 logarithmic scales. If log₁₀(1000) = 3, it means 10³ = 1000.
2. Natural Logarithm (ln)
The natural logarithm uses the mathematical constant e (approximately 2.71828) as its base. Natural logs are deeply connected to continuous growth and decay, making them essential in calculus, physics, and financial compounding calculations.
3. Binary Logarithm (log₂)
Using a base of 2, the binary logarithm is the foundation of computer science, information theory, and digital photography. It determines how many bits are required to encode a specific number of possibilities.
Properties of Logarithms
- Product Rule: log_b(x × y) = log_b(x) + log_b(y)
- Quotient Rule: log_b(x / y) = log_b(x) - log_b(y)
- Power Rule: log_b(xⁿ) = n × log_b(x)
- Change of Base: log_b(x) = log_c(x) / log_c(b) (This is how our calculator handles custom bases!)
Frequently Asked Questions
Can I find the logarithm of a negative number?↓
No. In the real number system, the domain of a logarithmic function is strictly positive numbers (x > 0). You cannot calculate the logarithm of a negative number or zero.
What does it mean if my log result is negative?↓
A negative logarithm result simply means the original number was a fraction between 0 and 1. For example, log₁₀(0.1) = -1, because 10⁻¹ = 0.1.
How do you calculate a logarithm with a custom base?↓
We use the Change of Base formula: log_b(x) = ln(x) / ln(b). Our calculator automatically applies this to evaluate custom bases instantly.