Curve Number Calculator

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.