by Mark Logarithm Calculator Logarithm Calculator Number (x) Must be a positive number Base (b) Base must be positive and ≠ 1 Log₁₀ (Common) Logₑ (Natural) Custom Base Logarithm Properties logₐ(xy) = logₐx + logₐy logₐ(x/y) = logₐx – logₐy logₐ(xⁿ) = n·logₐx logₐa = 1 logₐ1 = 0