Calculate the required drill size for LPG/Propane burners
Standard Propane pressure is usually 11″ WC.
BTU output drops roughly 4% per 1,000 ft.
Calculated Results:
Orifice Diameter (Inches):
Orifice Diameter (mm):
Recommended Drill Size (DMS):
Understanding Propane Orifice Sizing
When converting an appliance from natural gas to propane, or building a custom burner for a forge, smoker, or brewery, the most critical component is the orifice size. The orifice is the small brass fitting with a precision-drilled hole that regulates the flow of gas into the burner tube.
The Relationship Between Pressure and BTUs
Propane systems typically operate at a higher pressure than natural gas. While natural gas usually runs at 3.5″ to 7″ Water Column (WC), Propane (LPG) is standardly regulated to 11″ WC. Because propane has a higher energy density (approx. 2,500 BTU per cubic foot vs. 1,000 BTU for natural gas), the orifice for propane must be significantly smaller than a natural gas orifice for the same BTU rating.
How to Use This Calculator
Determine Target BTUs: Look at the burner's rating. If you want 30,000 BTUs of heat, enter that value.
Verify Pressure: Check your regulator. Most residential LPG regulators are set to 11″ WC. High-pressure adjustable regulators can go from 1 PSI to 20 PSI (Note: 1 PSI = 27.7″ WC).
Account for Altitude: If you are above 2,000 feet, your burner requires less fuel because the air is thinner. This calculator adjusts the required diameter to maintain a proper fuel-to-air ratio.
Propane Orifice Drill Chart Example
Orifice sizes are often referred to by Number Drill Sizes (DMS). Here is a reference for common propane burner outputs at 11″ WC:
10,000 BTU: #72 Drill (0.0250″)
20,000 BTU: #65 Drill (0.0350″)
40,000 BTU: #56 Drill (0.0465″)
60,000 BTU: #54 Drill (0.0550″)
Safety Warning
Working with gas components carries inherent risks. Always check for leaks using a soapy water solution after installing a new orifice. An orifice that is too large will cause "yellow tipping" and carbon monoxide production due to incomplete combustion (too rich). An orifice that is too small will result in a weak, lifting flame (too lean).