The aim of this work is to introduce a precise definition of the field capacity that is based on the moisture content, soil water potential and soil pore diameter. The concept uses the definitive relationships between the soil moisture content, soil matric suction and soil pore size. This approach is important as it would enable us to determine a more exact value of the field capacity for a given soil, rather than an approximate value that is traditionally based on some suction values of 0.1 or 0.3 bar or other values. The approach followed here depends on identifying the inflection point on the van Genuchten model of soil moisture-retention, and the relationship between soil matric suction and soil pore diameter.   Soil samples representing each of three regions in northern Egypt namly Nubaria, Borg El- Arab, and Edko were collected. The regions are. These regions represent different types of the newly reclaimed soils. In each site, three profiles were dug and different layers of each profile were sampled. The soils of these three regions differ in many characteristics and have different textures. The results showed field capacity values (volume basis) of 0.2275, 0.2380, and 0.3610 for the Nubaria, Borg El-Arab, and Edko soils; respectively. These values were found to be associated with soil matric suction values of 62, 186, and 308 mbar, and with soil pore diameters of 60, 16, and 14 μm, for the three soils , respectively. Different correlations between soil field capacity values and some soil physical properties, namely the total porosity, the bulk density and sand and clay contents, reflected high significance and showed high determination coefficients.