It is foreseen that ITER will employ a number of discrete limiters for the start-up and ramp-down phases of each discharge as well as for protection of the main wall during the diverted phase. Predictions are required of the radial power e-folding length, λq, in order to estimate the power loading on the limiters. This 3D problem has been addressed by Kobayashi et al (2007 Nucl. Fusion47 61–73) using a numerical edge code, EMC3-EIRENE. An analytic 3D model is presented here which well approximates the code calculations of λq, providing simple and convenient expressions for λq in terms of the shape and number of discrete limiters.