Magnetic Susceptibility Mapping is moving closer to clinical application. To reduce scan time, clinical images are often acquired with reduced resolution and coverage in the through-slice dimension. The effect of these factors has been studied using only balloon phantoms and downsampled brain images. Here, we used MR images acquired at low resolution or low coverage and compared these with images simulated in volunteers and a realistic numerical phantom. Simulated susceptibility maps were very similar to maps from acquired images. Our results show that low resolution and very low coverage both lead to loss of contrast and errors in susceptibility maps.