Drainage Pipe Sizing Tool

📏 Drainage Pipe Sizing Tool

Quickly size drainage pipes using Manning’s Equation + Rational Method.

This spreadsheet is designed for civil engineers, interns, and stormwater professionals who need to estimate the maximum allowable basin area for a proposed storm pipe — based on common assumptions used in land development.

✅ What It Does:

• Calculates pipe flow capacity using Manning’s Equation
• Uses the Rational Method to estimate max drainage area for a pipe
• Lets you customize pipe size, slope, roughness coefficient, intensity, and runoff 'c' factor
• Helps you select appropriate pipe sizes for residential or commercial land development

📊 Included:

• Table of pipe sizes (12" to 60") with corresponding flow capacities
• Pre-set assumptions (editable) for slope, Manning’s n, and Rational method values
• Step-by-step breakdown of calculations and terms
• Clean layout with editable cells highlighted for easy use

💡 Use This Tool To:

• Estimate drainage basin areas based on full-flow capacity
• Communicate pipe sizing logic
• Train junior staff or interns on stormwater basics

🔐 Note:

This spreadsheet was developed independently and does not reference any proprietary tools. It is intended for educational and professional reference only.

Disclaimer:

This tool was developed independently using general engineering knowledge, public-domain formulas, and personal experience. It does not use or reference any proprietary materials or confidential resources. Use of this spreadsheet is at the discretion of the user, who is responsible for verifying all calculations and assumptions.

All units are Imperial [US].