Gas Pipe Sizing
BTU capacity by pipe size, length, gas type.
Example
You enter
- BTU load (BTU/hr) 100000
- Pipe length (ft) 50
- Gas natural_gas
You get
- Required capacity 97.1 ft^3/hr
- Recommended size 0.75
Checked against published worked examples from: NFPA.
Details, formula, and sources
Formula or tableIFGC Equation 4-1 (low pressure, under 1.5 psi), D = Q^0.381 / (19.17 (dH / (Cr L))^0.206), solved for Q -- the relation Tables 402.4(1)-(36) are generated from -- sizing a SINGLE run of the entered length: it picks the smallest listed diameter whose capacity meets the load. Cr 0.6094 natural gas, 1.2462 undiluted propane. This is a single-segment estimate, NOT the full IFGC 2027 Section 402.4 / Tables 402.4(1)-(36) longest-length network method; a multi-branch system is sized on the single longest run to the most remote appliance, which the AHJ and the tables govern.
Source and editionIFGC 2027 (International Fuel Gas Code) / NFPA 54. Section 402.4 and capacity tables.
Free accessFree read-only access at codes.iccsafe.org. NFPA 54: Free read-only access at nfpa.org/freeaccess.
What governsEstimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.
API field namesbtu_load, length_ft, gas, required_cfh, recommended_size
- Pressure-drop allowance 0.5 in WC (low-pressure) / 1.0 psig (medium-pressure) unless user suppliesIFGC 2027 Section 402.3
- Gas factor Cr 0.6094 natural gas (SG 0.60) / 1.2462 undiluted propane (SG 1.52)IFGC 2027 Table 402.4