Just discovered that paint has an automatic resize tool
I was doing it by hand before and could never get it quite right. The "select" button has multiple options one of which is resize. Change cm to pixels and then alter the size. If its a tall image do vertical first and vice versa for wider images. This is because it automatically calculates the proportions for you to maintain the image's original geometricity,
I just set vertical or horizontal to their maximum values as the smaller the image the more detail is lost