KaLiBat is a graphical toolbox to calculate the linear heat loss coefficient of a 2D thermal bridge, according to the European standards EN10211 and EN13370. A thermal bridge is a thermal discontinuity in the building wall. The resulting thermal loss can be reduced by a better insulation or the use of a thermal break. To avoid a great thermal loss associated with a thermal bridge, the linear heat loss coefficient has to be evaluated : then two solutions may be compared, the better one has the lowest coefficient. KaLiBat makes possible the treatment of a great number of cases by modification of materials, sizes, b coefficient of surrounding spaces, surface resistances (continuous variation of an "internal" temperature to an "external "temperature"). Parameters may be selected on the screen and a button launchs the calculation, and result is displayed, with its distribution on surrounding spaces. A report printing is possible. Accuracy : many comparisons evaluate the KaLibat accuracy to values lower than 30 % for slab-on-grade floors, and lower than 12 % for other configurations (until 15 / 20 % if a screed is taken into account). For the geometry displayed on the screen, calculation is performed by a finite volumes method with an automatic meshing.