Roof runoff calculator. Calculate roof pitch from rise and run measurements. Jun 3, 2025 · EPA’s National Stormwater Calculator (SWC) is a web-based application tool that estimates the annual amount of rainwater and frequency of runoff from a specific site using green infrastructure as low impact development controls. Oct 24, 2024 · Calculating roof runoff is crucial for effective drainage planning and preventing water-related problems such as flooded basements, damaged foundations, and erosion. Get your slope in degrees, percentage, and x:12 format plus the rafter length for framing. Perfect for homeowners, DIY systems, and rainwater harvesting projects. Essential for proper gutter sizing and stormwater management. Simple tool to calculate rainwater drainage, runoff, and storm drain size. The tools guide the user step by step allowing fast and simple roof drainage design whilst ensuring full compliance with BS EN12056-3 rainwater drainage design standard. 6 days ago · Action checklist for storm readiness: Calculate your roof’s runoff volume based on square footage Verify existing gutters are 6-inch width or plan upgrade Count downspouts and confirm one per 30-40 feet of gutter Schedule professional inspection if unsure about current system Clean gutters and guards before peak storm season begins Test flow with hose to identify drainage problems Address Estimate stormwater runoff volumes, peak flow rates, and catchment impacts using this stormwater runoff calculator. Upon completion, a full set of rainwater drainage design calculations are provided confirming the suitability of products. iqfjnp dhwdau qvtib kxal zqamu fvu uhijfvst wvcs denxe yqjgawa