Hydronic Pipe Size Calculator
Heating/cooling water pipe diameter from kW and ΔT at a sane velocity.
50 kW at ΔT10 flows 1.2 L/s → 32 mm pipe at 1.5 m/s. Small-bore noise limit: keep under ~1.2 m/s in occupied zones.
Formula
Hydronic Pipe Size Calculator is a free hydronic pipe sizing for HVAC designers, technicians and energy auditors — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Hydronic Pipe Size Calculator
Heating/cooling water pipe diameter from kW and ΔT at a sane velocity. The calculation implements Q = P/(c_p·ΔT); D = √(4Q/πV) (CIBSE Guide B; BSRIA rules of thumb). 50 kW at ΔT10 flows 1.2 L/s → 32 mm pipe at 1.5 m/s. Small-bore noise limit: keep under ~1.2 m/s in occupied zones.
How to use Hydronic Pipe Size Calculator
- 1Enter Thermal load in kW.
- 2Enter Water ΔT in °C.
- 3Enter Design velocity in m/s.
- 4Read Flow, Required ID instantly — no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Hydronic Pipe Size Calculator?
- ✓Implements the standard formula — Q = P/(c_p·ΔT); D = √(4Q/πV)
- ✓Reference cited on-page: CIBSE Guide B; BSRIA rules of thumb
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Hydronic Pipe Size Calculator use?+
It computes Q = P/(c_p·ΔT); D = √(4Q/πV), per CIBSE Guide B; BSRIA rules of thumb. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
50 kW at ΔT10 flows 1.2 L/s → 32 mm pipe at 1.5 m/s. Small-bore noise limit: keep under ~1.2 m/s in occupied zones.
Is this based on ASHRAE methods?+
The calculations follow the standard ASHRAE/ISHRAE formulations cited under the result, simplified where industry practice does the same. For permit-grade design, confirm with the full code procedure.
Is the Hydronic Pipe Size Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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