Using the distance formula:
\[
d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}
\]
Given points:
\[
A(1,-3) \quad \text{and} \quad B(4,-6).
\]
Substituting values:
\[
d = \sqrt{(4 - 1)^2 + (-6 + 3)^2}
\]
\[
= \sqrt{(3)^2 + (-3)^2}
\]
\[
= \sqrt{9 + 9} = \sqrt{18} = 3\sqrt{2}.
\]