PEX Pipe Dimensions

PEX is flexible plastic tubing sized like copper — the outside diameter is the nominal size plus 1/8 inch. This chart lists the common sizes and inside diameters.

Nominal OD (in) ID (in)
3/8 in 0.500 0.350
1/2 in 0.625 0.475
3/4 in 0.875 0.671
1 in 1.125 0.863
Color is convention, not rule. Red PEX is used for hot and blue for cold to keep runs organized, but the tubing is identical. 1/2 in serves most fixtures; 3/4 in feeds branches and manifolds.

See the Copper Pipe Dimensions and Fixture Flow Rate Chart.

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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.