Markov Random Field (MRF) is a probabilistic circuit design approach that transforms simple CMOS to MRF-CMOS digital circuits. The transformed circuits are proved to be extremely noise-tolerant in the previous research literature. In this paper, we have quantified the noise tolerance capability of MRF circuits as compared to CMOS counterparts. The tradeoff for this noise-immunity is the increase in transistor-count of the circuit. This tradeoff is modelled by a novel factor in this research work called as reliable area index. The results show that the value of this index is 30 times higher for MRF than CMOS which proves that the MRF design approach still maintains a suitable tradeoff between noise-tolerance and area overhead of the circuit. © 2011 IEEE.