National Stormwater Calculator

U.S. Environmental Protection Agency

abstract background image with blue overlay


This software application tool estimates the annual amount of rainwater and frequency of runoff at a specific site using green infrastructure as low-impact development controls.

National Stormwater Calculator Homepage


  • Analyzes site hydrology for small- to medium-sized locations (less than 12 acres)
  • Accesses several national databases that provide soil, topography, rainfall, and evaporation information for a chosen site
  • Shows how runoff may vary based on historical weather and potential future climate conditions