Power Calculators

log Logarithm Calculator

Calculate a logarithm with a custom base.

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Also available in our Android app, with charts and full breakdown tables.

📘 About the Logarithm

Uses the change-of-base formula.

🧮 Formula

Where

  • log_b(x) = ln(x) / ln(b)
Number and base must be positive; base cannot be 1.

✏️ Worked example

log base 10 of 100

You enter
Number100
Base10

The answer is {result}.

Try this example →

🧭 How to use this calculator

What you enter

  • Number
  • Base

What you get

  • Logarithm
  • Valid Input

💡 Common uses

  • School mathematics and algebra
  • Scientific calculations
  • Engineering and measurement

❓ Frequently asked questions

Can the base be 1?

No. A logarithm base must be positive and not equal to 1.