We investigate thermal transport on microcontacts established between two silicon wedges. The measurements are carried out with a variable contact radius of 0.3--2 \ensuremath{\mu}m at temperatures from 2 to 300 K. The measured thermal resistance is used to calculate the contact radius with an accuracy better than 50%. Comparison of electrical and thermal transport indicates the existence of a tunnel barrier between the contact legs. Electrical measurements are therefore unreliable to determine the contact size.