This paper presents experimental results of quantitative DC measurements carried out by the use of a scanning thermal microscope equipped with nanofabricated thermal probes, and their numerical simulations done by finite element analysis. In the proposed method, the probe resistance variations are measured for the sampleto-air transition. It is shown that taking the signal measured in air as a reference makes the measurement less sensitive to instabilities of ambient conditions. This paper also presents a simple theoretical model describing the phenomena associated with heat transfer in the probe-sample system. Both experimental and numerical results confirm the theoretical findings. The registered signal can be related to the thermal conductivity of different materials, which makes the method useful for determining the local thermal conductivity.