The distance of a point \( (x, y) \) from the origin \( (0, 0) \) is given by the distance formula:
\[
\text{Distance} = \sqrt{x^2 + y^2}
\]
Substituting the coordinates \( P(-6, 0) \) into the formula:
\[
\text{Distance} = \sqrt{(-6)^2 + 0^2} = \sqrt{36} = 6
\]
Final Answer: 6.