For jointed plain (unreinforced) concrete pavement (JPCP), the maximum allowable joint spacing or slab length depends on variables such the slab thickness, concrete aggregate used, cement content, subgrade/subbase used, and climate. In most areas, the typical maximum transverse joint spacing for JPCP used in applications such as streets, roads, and highways is about 15 ft (4.5 m); a longer maximum transverse joint spacing may be used, however, based on local experience. Longitudinal joint spacing on two-lane and multilane concrete pavements typically is about 10 to 13 ft (3.0 to 4.2 m). This tool provides an estimate of the maximum allowable joint spacing based on the slab thickness and the subgrade/subbase used, two of the variables with the most prominent effect on joint spacing requirements. Slabs kept to dimensions shorter than those calculated by this tool will have curling and warping stresses within safe limits to ensure minimal risk of random cracking.