How to Calculate Pipe Sizing
What is Pipe Sizing?
Pipe Sizing Calculator helps contractors and tradespeople accurately size, spec, and estimate materials and systems.
Formula
Min Diameter = √(4Q / π × V) where Q=flow, V=max velocity
Step-by-Step Guide
- 1Determine required flow rate, select acceptable velocity, solve for diameter
- 2Apply the formula using your project measurements
- 3Add required safety factors or waste allowances per code
Worked Examples
Input
50 GPM flow, 6 fps max velocity
Result
D = √(4×0.111/(π×6)) = 0.154 ft = 1.85 inches → use 2 inch
Common Mistakes to Avoid
- ✕Not applying code-required safety factors or derating
- ✕Forgetting to account for waste and cut losses in material estimates
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