Gas Pipe Sizing Calculator
Size natural gas or propane pipes by BTU load and pipe length. Supports 2 PSI, 0.5 PSI, and 14-inch WC systems per IFGC standards.
BTU/hr
ft
Minimum Pipe Size
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Capacity at That Size —
Approx. Gas Velocity —
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BTU/hr
ft
Minimum Pipe Size
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Pipe Capacity —
Professional Full parameters & maximum detail ▾
BTU/hr
ft
ft
%
Sizing Inputs
Total Equiv. Length —
Design Load (with safety) —
Result
Required Pipe Size —
Pipe Capacity —
Notes
Material Note —
How to Use This Calculator
- Enter the total BTU load (sum of all appliances on this run).
- Enter the pipe run length in feet.
- Select inlet pressure. Results show minimum pipe diameter.
Formula
Based on IFGC Table 402.4 (Schedule 40 black iron pipe).
Capacity varies by pressure, pipe diameter, and equivalent length. Higher pressure and shorter runs allow smaller pipe diameters.
Example
Example: 120,000 BTU total load, 30-ft run, 0.5 PSI inlet → minimum 3/4-inch pipe required.
Frequently Asked Questions
- Determine the total BTU demand of all appliances, measure the pipe run length, choose your operating pressure, and consult IFGC Table 402.4. This calculator automates that process.
- 14 inches water column (WC) is approximately 0.5 PSI, which is standard low-pressure residential gas service in the US.
- A typical gas furnace uses 60,000–120,000 BTU/hr. A water heater uses 30,000–50,000. A range uses 55,000. A dryer uses 20,000.
- Black iron pipe is traditional and code-compliant. CSST (corrugated stainless steel tubing) is flexible and faster to install. Both require proper fittings and bonding.
- Size the pipe for 100% of total load. Never undersize. Many inspectors require the pipe to carry 125% of calculated load.