Log Calculator
Compute the natural log ln, common log log10, or log base b of x.
Input Data
對數的真數（須 > 0）。
僅在選「自訂底數」時使用（須 > 0 且 ≠ 1）。
Results
2
log₁₀(100) = 2
At a glance:log_b(x) answers 'to what power is b raised to get x?'. Natural log uses e; common log uses 10. Change-of-base: log_b(x) = ln(x)/ln(b).
Formula
log_b(x) = ln(x) / ln(b).
ln(e)=1, log10(10)=1.
How to Use
- Enter x (>0).
- Pick a base or custom.
- Read the result.
FAQ
Why must x be > 0?
Real logarithms are defined only for positive numbers.
Can the base be 1?
No — 1 to any power is 1, so the log is undefined; base must be ≠ 1.
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References
Content review: Calculatorism Science Team. Results are for reference only.