Monte Carlo Simulation (MCS) method is used to evaluate the three classical formulations of fin efficiency and it has been identified that the conventional formulations either under estimate or over estimate the efficiency of typical fins. It is also shown that Gardner's model of fin efficiency holds good for a fixed point and for all values above this point, the model seems to under predict fin efficiency. It is also seen that the underlying assumptions in the model form the reason behind the same and the effect of violating each of the assumption is shown for all possible ranges of input values. A modified formulation for fin efficiency, eliminating the underlying assumptions, is also proposed. (c) 2005 Elsevier Ltd. All rights reserved.