Pipe volume calculator
Inside diameter and length: you get the water volume, its weight and litres per metre — for filling, purging or dosing.
Water volume
1.593 gal
- Water volume1.593 gal
- Water weight13.294 lb
- Litres per metre of pipe0.2 l/m
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How it's calculated (visible formula)
V = π/4 × D² × length
- Net geometric measurement, no waste.
- Adjustable waste % for cuts and breakage.
- Purchase rounded up to sellable units (boxes, bags, buckets, boards).
How to calculate it, step by step
- Measure or look up the inside diameter.
- Measure the total loop length.
- Work out inside area.
- Multiply by length for the volume.
- Add radiators, boiler or tanks for a whole system.
Worked example: 100 ft loop of ⅝ in (16 mm ID) pipe
- π/4 × 0.016² = 0.000201 m²
- × 30 m × 1000
→ 1.6 gal (6.03 l).
Common mistakes
- Using the outside diameter.
- Forgetting boiler and radiator volume in heating systems.
- Not counting glycol as a share of the total.
Pro tips
- Use total volume to dose inhibitor (often 1 l per 100 l).
- Glycol percentage depends on the lowest expected temperature.
- Bleed air from high points after filling.
- Write the volume on the boiler for future service.
From calculation to quote
Add labor, overhead and your margin, and generate the professional PDF.
FAQs
- How much water in ½ in PEX per foot?
- About 0.0092 gal per foot.
- What is this used for?
- Dosing inhibitor or glycol and sizing expansion tanks.
- Radiant floor tubing?
- ½ in PEX holds about 0.92 gal per 100 ft.
- How much water does a radiator hold?
- Roughly 1–4 gallons depending on size.
- How much glycol should I use?
- About 30% propylene glycol protects to roughly 5 °F.
- Why know system volume?
- To dose additives, size the expansion tank and plan purging.
Sources and standards
Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.