Pipe Size Calculator
Residential water supply pipes should carry water at 2–8 ft/sec to prevent noise and erosion. Enter your required flow rate and pipe material to get the minimum pipe diameter and recommended size from standard schedules.
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Top Pick3/4" Copper Type L Pipe — Home Depot~$12/10 ft* Affiliate links — we may earn a commission at no cost to you.
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How to Use This Calculator
- 1Enter your measurements in the fields above. Use the units shown next to each field (ft, in, etc.).
- 2Click Calculate to get your material estimate instantly.
- 3Review the highlighted result — it shows the key quantity you need to order.
- 4Use Copy Results to save your estimate, or bookmark the URL — your inputs are encoded in the link.
Pro tip: Always add 10% to your material order to account for waste, cuts, and defects.
Frequently Asked Questions
What pipe size do I need for a residential main water line?
Most residential main lines use 3/4" or 1" pipe. At a peak demand of 10 GPM, a 3/4" copper pipe carries water at ~7 ft/sec — within the 8 ft/sec limit. For homes with high fixture counts (5+ bathrooms), use 1" main lines.
Why does pipe velocity matter?
Velocity above 8 ft/sec causes water hammer noise, erosion at fittings, and premature pipe failure. Below 2 ft/sec, sediment can accumulate in hot water lines. The sweet spot is 3–6 ft/sec for supply lines.