# Squared length of 4-momentum g(p,p)?

Homework Statement:
Can someone explain why the squared length of p^2 = p dot p = -m^2 and not -m^2*c^2?
Relevant Equations:
p^2 = p dot p = -m^2
Explained in statement.

Gaussian97
Homework Helper
That depends on two things:
1. What is the metric you use

2. What are the units you are using.

PeroK