Logarithm Calculator

This calculator finds the logarithm of any number to any base, along with two commonly used variants: the natural log (ln) and log base 10. A logarithm answers a simple question: what power must the base be raised to, to produce this number. It is the mirror image of an exponent, and understanding it helps with science and engineering formulas, interest rate maths, and data analysis. You enter two figures: the number you want the logarithm of, and the base you want to use. As soon as you type, the calculator works out the answer using the change of base rule, dividing the natural log of the number by the natural log of the base, and displays the result under a clear label showing exactly which log you have calculated, for example log base 2 of 1,000. Alongside the main result, it also shows the natural log and the log base 10 of your number, so you can compare all three at once without re-entering anything. The number must be greater than zero, and the base must be positive and cannot equal one, since logarithms are undefined outside these limits, and the calculator will flag it if either rule is broken. Try it with the default values of 1,000 and base 10 to see how the familiar result of 3 is produced, then swap in your own figures.

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