The rate at which low-mass stars lose angular momentum on the main sequence depends strongly on their magnetic characteristics. In recent years, there has been an increasing focus on how magnetic field geometry affects stellar spin down. This is a problem that Zeeman-Doppler imaging (ZDI) is well suited to addressing since it is capable of capturing the large-scale magnetic field structure at the stellar surface. In this talk I estimate the angular momentum-loss rates for a sample of stars that have had their magnetic fields mapped with ZDI. Additionally, I will discuss these results in the context of long term rotation period evolution.