Two simple calculation methods are proposed to estimate spatially averaged LAeq of an evaluation section, parallel to an arterial road at ground level, in a built-up area. In the methods, buildings in the area are classified into the first row of buildings (FRB) directly facing the road and the rear group of buildings (RGB) behind it. With regard to parameters for calculation, the first method takes into account the spacing of FRB and the density and width of RGB, whereas the second only takes into account the average density of buildings existing in the whole built-up area. Field surveys in 33 built-up areas all over Japan were conducted to verify the validity of the calculation methods. As a result, both the first method, giving a little higher accuracy, and the second one can be applied to predict and evaluate noise in large areas along the roads.