Dipole moment - calculation of percentage ionic character

Question: The dipole moment of $\ce{HBr}$ is $2.60 \times 10^{-30}$ and the interatomic spacing is $1.41$. What is the percentage ionic character of $\ce{HBr}$?

What I know is that the percentage ionic character is observed dipole moment divided by calculated dipole moment $\times\ 100$.

The calculated dipole moment is $\textrm{charge on electron} \times \textrm{radius of molecule}$.

However, how would I convert interatomic spacing into radius?