The Curve Number Calculator allows the curve number to be calculated for the SCS runoff method.
Land Use – The primary category of the land use. Urban Areas, Cultivated Agricultural Lands, Other Agricultural Lands, or Arid & Semiarid Rangelands.
Cover Type – The specific type of cover on the land use. Options available depend on Land Use.
Condition – The hydrologic condition of the land use. Options available depend on Cover Type.
Soil Group – The hydrologic soil group of the Soil Type. A, B, C or D.
Pervious Curve Number – As different options are selected from the drop-down list, the appropriate curve number is selected. Clicking OK will select the currently displayed curve number.
Curve Numbers are calculated by looking up the values in the tables 2-2a to 2-2d in document TR-55.pdf, authored by Natural Resources Conservation Service (NRCS). TR-55 is a widely-used approach to hydrology in the US.