We show the possibility to measure the effective tip shape and the lateral resolution of a scanning force microscopy (SFM) probe on the nanometer-scale directly from SFM images of SiC(0001). On this surface there are grooves 10–100-nm-wide related to cleavage planes. The SFM tip penetrates the groove but does not reach the bottom since its side walls touch both rims. The width of the narrowest groove resolved is the lateral resolution. The apparent topography across a groove yields directly the tip radius of curvature in excellent agreement with the values estimated from scanning electron micrographs. © 1997 American Institute of Physics.