PIPE VOLUME
PIPE VOLUME
V = π·r²·L ÷ 231
in
ft
RESULT
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Calculates a single straight pipe run. Multiply by number of runs as needed.
About this calculator
This pipe volume calculator gives the water capacity of a single straight pipe run in gallons, cubic inches, and liters. Useful for sizing water heaters, calculating purge volumes for plumbing, or estimating fill time. Multiply the result by the number of identical runs for total system volume. Diameter is the inside diameter (ID), not the nominal size.
Common questions
Why do I need to know pipe volume?
Sizing water heaters (recovery time), purging air or sediment, calculating chemical treatment doses, fill times for new systems, and estimating leak losses. Also useful for hydronic heating loop calculations.
What's the difference between pipe ID and OD?
ID is inside diameter (the water-carrying area). OD is outside diameter (the wall-to-wall measurement). For volume calculations, always use ID. Nominal pipe size (NPS) is neither — it's a label, not a measurement.
How much water is in 100 ft of ½" pipe?
Type L copper ½" pipe (ID 0.545") holds about 1.21 gallons per 100 ft. PEX-A ½" (ID 0.475") holds 0.92 gallons. Schedule 40 PVC ½" (ID 0.602") holds 1.48 gallons. Always check actual ID — it varies by material.