Propane to Natural Gas Conversion Calculator: Orifice Size, BTU, and Drill Bit Guide
Key Takeaways
- Natural gas has roughly 41 percent of the BTU density of propane by volume, so the replacement orifice must be approximately 1.6 times larger in diameter to maintain the same heat output.
- Both the burner orifice and the gas regulator must be replaced during conversion; changing only the orifice is not a complete or safe conversion.
- Portable fire pits and most propane grills are not convertible to natural gas; fixed fire pit tables and stationary outdoor fireplaces typically are, with a manufacturer-approved conversion kit.
- At US average fuel prices, a 60,000 BTU fire pit costs approximately $2.30/hr on propane versus $0.69/hr on natural gas, a saving of roughly $1.60/hr or $320 per 200-hour season.
- All gas line work and appliance connections must comply with NFPA 54 (National Fuel Gas Code) and local permit requirements.
Use this propane to natural gas conversion calculator to find the correct burner orifice diameter for your fire pit or outdoor appliance in decimal inches, millimeters, and the nearest standard drill bit number. Enter your BTU rating to get the orifice size, a fuel cost comparison in dollars per hour, and a personalized product recommendation based on your appliance type.
Unlike static BTU lookup tables or utility-company billing calculators, this tool is designed specifically for fire pit and outdoor appliance conversions. Use it to convert propane to natural gas, or to handle natural gas to propane conversion when moving from utility service back to a tank. The orifice output is based on empirical gas flow constants validated against industry drill size charts, using standard manifold pressure values of 11 inches WC for propane and 3.5 inches WC for natural gas.
Propane to Natural Gas Conversion Calculator
Find this on the appliance label, in the manual, or stamped near the burner assembly.
Optional: Fuel Cost Estimate
Used to calculate annual fuel savings at US average prices (propane $3.50/gal, NG $1.20/therm).
Decimal inch diameter
Select your current drill size
Please complete all required fields before calculating.
New Orifice Diameter
decimal inches
Metric Equivalent
millimeters
Nearest Drill Bit
Orifice diameter calculations are estimates based on empirical gas flow constants for standard residential manifold pressures (propane: 11 inches WC; natural gas: 3.5 inches WC) and published BTU content values (propane: 2,516 BTU/ft³; natural gas: 1,030 BTU/ft³). Fuel cost estimates use US average prices (propane: $3.50/gallon; natural gas: $1.20/therm) and may vary significantly by region and season. Always use a manufacturer-listed conversion kit and the orifice size specified in that kit, not a field-calculated size, for any gas appliance conversion. All gas appliance conversions must comply with NFPA 54 and local Authority Having Jurisdiction requirements.
Can You Convert Propane Fire Pit to Natural Gas?
Most fixed propane fire pits can be converted to natural gas, but the answer depends on whether the manufacturer has produced a listed conversion kit for your specific model. The conversion requires replacing three components: the burner orifice, the gas regulator, and the supply hose. Changing the orifice alone is not a complete or safe conversion.
Portable propane fire pits cannot be converted to natural gas. A natural gas connection requires a permanent piped supply from the utility line, which means the appliance must be fixed in place. If your fire pit uses a quick-disconnect propane hose attached to a portable tank, it is not convertible.
Fire pit tables, in-ground fire pits, and stationary built-in outdoor fireplaces are the most commonly convertible appliances. For each of these, the first step is confirming the manufacturer offers a listed conversion kit. Using a third-party orifice not specified for your appliance model carries liability risk and may void the warranty.
Natural Gas Conversion Kit for Fire Pits: What the Kit Includes
A fire pit natural gas conversion kit typically contains three components. The first is the replacement brass orifice, sized for natural gas at 3.5 inches WC manifold pressure to match the appliance's rated BTU output. The second is a natural gas pressure regulator, which replaces the propane regulator and reduces incoming gas pressure to the correct manifold pressure. The third is a flexible gas connector hose with the correct fittings for the appliance inlet and the gas valve.
Some kits also include a new gas valve rated for natural gas, a new burner pan or tray, and hardware for securing the flex line. The total cost of a manufacturer-supplied kit runs $50 to $200 depending on the brand. Installation requires connecting to an existing natural gas supply line at the patio, which typically requires a licensed plumber or gas contractor to run the gas line extension and make the final connection.
If your fire pit model does not have a manufacturer conversion kit available, the safest path is purchasing a new natural gas fire pit rather than attempting a field conversion. Browse gas fire pits that are designed and plumbed for natural gas from the factory, which eliminates the conversion process entirely for new purchases.
Propane vs. Natural Gas Fire Pit: Fuel Cost Comparison
The decision to convert is often as much about ongoing cost as it is about installation effort. Natural gas costs significantly less per BTU than propane in most U.S. regions, and the savings compound quickly on a high-output appliance used frequently.
| BTU Rating | Propane Cost/hr ($3.50/gal) | Natural Gas Cost/hr ($1.20/therm) | Annual Savings (200 hrs/season) |
|---|---|---|---|
| 40,000 BTU | $1.53/hr | $0.46/hr | ~$214/season |
| 60,000 BTU | $2.30/hr | $0.69/hr | ~$322/season |
| 80,000 BTU | $3.06/hr | $0.93/hr | ~$426/season |
For a deeper comparison including installation considerations, appliance selection, and which fuel wins for each use case, see the full guide on propane vs natural gas fire pits. To shop by fuel type, browse propane fire pits across all styles and BTU ranges.
What Orifice Size Do You Need When Converting Propane to Natural Gas?
The burner orifice is the precision-drilled hole through which gas flows into the burner assembly. The orifice controls how much gas enters the burner and, combined with manifold pressure, determines BTU output. When converting between fuels, the orifice must be resized because propane and natural gas have different energy densities and operate at different pressures.
Natural gas contains approximately 1,030 BTU per cubic foot. Propane contains approximately 2,516 BTU per cubic foot. To deliver the same BTU output, a natural gas burner must pass roughly 2.44 times the volume of gas per hour compared to propane. Natural gas also operates at lower manifold pressure: 3.5 inches water column (WC) versus 11 inches WC for propane. Both factors mean the natural gas orifice must be substantially larger.
The practical conversion ratio, derived from gas flow physics and validated against industry drill size charts, is: natural gas orifice diameter equals propane orifice diameter multiplied by approximately 1.62. Converting in the other direction, a propane orifice is approximately 0.62 times the diameter of the natural gas orifice for the same appliance. The Orifice Converter tab functions as a gas orifice size calculator: enter your current drill number or decimal diameter and the tool returns the converted size in decimal inches, millimeters, and the nearest standard drill bit number.
The BTU Difference Between Propane and Natural Gas
Understanding BTU content explains why the orifice must change size and why the regulator must also be replaced.
| Property | Propane (LP) | Natural Gas (NG) |
|---|---|---|
| BTU per cubic foot | 2,516 BTU | 1,030 BTU |
| Specific gravity (vs. air) | 1.52 | 0.60 |
| Standard manifold pressure | 11 inches WC | 3.5 inches WC |
| BTU per gallon (liquid) | 91,547 BTU | N/A (sold by volume or therm) |
| BTU per therm (100 ft³) | N/A | 103,700 BTU |
| Relative orifice size needed | Smaller (baseline) | Approx. 1.62x larger diameter |
A common misunderstanding is that converting from propane to natural gas reduces the BTU output of the fire pit. It does not, provided the conversion is done correctly with a properly sized orifice and the correct regulator. The larger orifice at lower pressure delivers exactly the same volume of combustible energy per hour as the smaller propane orifice at higher pressure.
Combustion engineers also compare fuels using the Wobbe index, which is calculated as the calorific value divided by the square root of specific gravity. Propane has a Wobbe index of approximately 1,367 BTU/scf; natural gas runs approximately 1,327 BTU/scf. The close Wobbe index values confirm why a properly resized orifice and regulator produce stable, equivalent combustion on either fuel without burner redesign.
To estimate propane consumption before or after conversion, use the propane usage calculator, which calculates runtime and tank usage from appliance BTU rating and tank size. To convert your natural gas bill units (therms, CCF, MCF) into BTU, use the natural gas BTU calculator.
How to Convert a Propane Fire Pit to Natural Gas: Process Overview
The conversion process has five steps. Understanding each step helps you evaluate whether to handle the project yourself or hire a contractor.
- Confirm convertibility. Contact the fire pit manufacturer with your model number and ask whether a listed natural gas conversion kit is available. If no kit exists, stop here.
- Arrange the gas line. A licensed plumber or gas contractor must extend the natural gas supply line from the nearest house connection point to the patio location. This step requires a permit in most jurisdictions and cannot be done by the homeowner in most states. The contractor also installs the shut-off valve at the patio termination point.
- Install the conversion kit. The kit typically includes the new brass orifice, gas regulator, and flex connector. Installation involves removing the propane components, installing the new orifice in the burner assembly, connecting the new regulator to the gas valve, and attaching the flex line to the shut-off valve. In most jurisdictions, this work on the appliance side can be performed by a competent DIYer using the manufacturer instructions, though local codes vary.
- Leak test. Before lighting the appliance, apply an approved leak detection solution or electronic gas detector to every connection point. Any bubbling indicates a leak that must be corrected before use. Never use an open flame to check for gas leaks.
- Test fire and flame quality check. Light the burner and observe the flame. A properly converted natural gas fire pit produces a steady blue-tipped flame with yellow highlights. A bright yellow or orange flame with black soot indicates incomplete combustion, which may signal an orifice that is too large or a regulator pressure that is too high.
Frequently Asked Questions
Can I convert my propane fire pit to natural gas?
Most fixed fire pits can be converted to natural gas with a manufacturer-approved kit including a replacement orifice and regulator. Portable fire pits are not convertible since they need a permanent gas line. Confirm a listed kit exists for your specific model first.
What orifice size do I need when converting propane to natural gas?
The natural gas orifice diameter should be approximately 1.62 times the propane orifice diameter. Enter your existing drill number or decimal size in the Orifice Converter tab above. The result shows decimal inches, millimeters, and the nearest standard drill bit.
Is it worth converting a propane fire pit to natural gas?
If you have a natural gas line and use the fire pit regularly, conversion is typically worthwhile. Natural gas costs roughly one-third the per-BTU price of propane in most U.S. markets. A $50-$200 kit plus gas line work is usually recovered within two seasons.
What is the BTU difference between propane and natural gas?
Propane delivers 2,516 BTU per cubic foot; natural gas delivers 1,030 BTU per cubic foot. A correctly converted appliance produces identical BTU output on either fuel. The orifice change and regulator swap together compensate for the difference in energy density and pressure.
Do I need a regulator when converting propane to natural gas?
Yes. Propane runs at 11 inches WC manifold pressure; natural gas runs at 3.5 to 7 inches WC. You cannot reuse the propane regulator. Most manufacturer conversion kits include the replacement regulator, new orifice, and flex hose as a complete set.
How much does it cost to convert a fire pit from propane to natural gas?
Conversion kits from the manufacturer typically cost $50 to $200. Running a new gas line from the house to the patio adds $300 to $1,000 in licensed contractor fees and permit costs. Total for most residential conversions falls between $400 and $1,200.
Can all propane appliances be converted to natural gas?
No. Portable fire pits, portable heaters, and most gas grills are not designed for conversion. Fixed fire pit tables, outdoor fireplaces, and stationary patio heaters with manufacturer-approved kits can typically be converted. Always confirm a listed kit exists for your specific model.
Related Calculators and Tools
- Propane Usage Calculator: estimate tank runtime and annual propane cost by appliance BTU rating and usage hours.
- Propane vs. Natural Gas Fire Pits Guide: full comparison of both fuels covering cost, installation, appliance selection, and which fuel wins for each use case.
Ready to Make the Switch?
Running this propane to natural gas conversion calculator takes 30 seconds and gives you the exact orifice diameter, the $/hr cost comparison, and a product recommendation before you order a kit or call a contractor. The two most common conversion mistakes are ordering the wrong orifice size and forgetting to replace the regulator. The calculator output covers both.
If you are starting with a new purchase rather than converting an existing unit, natural gas fire pits and natural gas fire tables arrive factory-configured for NG with no conversion required and a dedicated gas valve, regulator, and properly sized orifice already installed.
