Propane Orifice Size Calculator

Estimate exact propane burner orifice diameter, match the closest numbered drill bit, and review per-burner flow using regulated manifold pressure, burner count, and LP gas constants.

Built for burner math

Sizes one propane orifice per burner from total BTU load, pressure, fuel properties, and discharge coefficient instead of guessing from a single chart row.

Dual unit workflow

Switch between inches water column and kPa for pressure while the results always show both inch and millimeter diameter outputs for easy drill matching.

Useful outputs

Review recommended diameter, nearest drill, per-burner input, propane draw, and how an existing drilled hole compares to the target capacity.

📌Scenario Presets

⚙Burner Inputs

Imperial inputs Metric pressure and hole size

Appliance profile Profiles only set typical starting values. You can override any field below.

Total appliance input (BTU/hr) Enter the full appliance heat input before it is split across burners.

Number of burner orifices Most grill manifolds use one fixed orifice per burner tube.

Manifold pressure (in. W.C.) Baseline LP charts are commonly published at 11 inches water column.

Design margin Add a small load reserve before choosing the nearest standard drill size.

Discharge coefficient The reference LP drill chart used here is normalized around a 0.80 coefficient.

Propane specific gravity Default matches common LP vapor tables. Heavier gas lowers capacity for the same hole.

Heating value (BTU per ft3) Used to convert BTU demand into propane vapor flow in cubic feet per hour.

Existing orifice diameter (inches, optional) Leave blank to skip comparison against an already-drilled orifice.

Reference drill size Useful when you know the numbered drill but not the actual inch value.

This calculator uses an LP baseline of 2500 BTU per cubic foot, specific gravity 1.53, and a chart-normalized coefficient of 0.80, then adjusts diameter from your actual pressure, gas properties, and burner split.

Recommended Hole

0.0000 in

0.00 mm finished diameter

Nearest Drill

#00

0.0000 in actual diameter

Per-Burner Load

0 BTU/hr

0.00 CFH propane vapor

Total Propane Draw

0.00 gal/hr

0.00 lb/hr and 0.00 CFH total

Calculation breakdown

Enter values and calculate to see the full LP sizing path.Waiting

📊Propane Reference Grid

11 in.

Standard LP Pressure

Common appliance manifold pressure used by published low-pressure LP drill charts.

2.74 kPa

Metric Pressure Pair

Direct metric equivalent for 11 inches water column during manifold checks.

2500

BTU Per Ft3

Reference propane vapor heating value used for cubic-foot flow calculations.

1.53 SG

Specific Gravity

Baseline density relationship behind the published LP capacity chart.

0.80

Reference Cd

Discharge coefficient baked into the baseline drill-size versus BTU table.

91500

BTU Per Gallon

Useful for converting total burner demand into liquid propane gallons per hour.

21590

BTU Per Pound

Used here to show mass consumption for cylinders and bulk LP planning.

25.4 mm

Per Inch

Converts exact orifice diameter into metric drill values without changing BTU math.

📋Low-Pressure LP Drill Capacity Table

Drill Size	Diameter (in.)	LP BTU/hr at 11 in. W.C.	Typical Match
#70	0.0280	5,490	Pilot scale burners
#67	0.0320	7,150	Very small hob
#64	0.0360	9,050	Compact cooktop
#61	0.0390	10,600	Small furnace pilot main
#58	0.0420	12,300	Utility burner
#56	0.0465	15,100	Side burner
#54	0.0550	21,200	Smoker burner
#52	0.0635	28,200	Furnace burner
#50	0.0700	34,200	Heater burner
#48	0.0760	40,400	Tall patio heater
#46	0.0810	45,800	Large fryer
#44	0.0860	51,600	Fire pit ring
#42	0.0935	61,100	High output ring
#38	0.1015	72,000	Forge burner
#34	0.1110	86,200	Large single burner
#30	0.1285	115,300	Very high output

🔍Appliance Comparison Table

Appliance	Total Input	Burners	Common Drill Result
Range top burner	9,500 BTU/hr	1	#64 to #61
Smoker burner	18,000 BTU/hr	1	#55 to #54
3-burner grill	36,000 BTU/hr	3	#58 per burner
Side burner	12,000 BTU/hr	1	#58 to #56
RV furnace	30,000 BTU/hr	1	#52 to #50
Patio heater	40,000 BTU/hr	1	#48 to #46
Fire pit ring	65,000 BTU/hr	1	#42 to #40 range
Dual wok station	120,000 BTU/hr	2	#42 per burner

📏Common Burner Load Table

Scenario	Pressure	Primary Result	Secondary Result
Single range burner	10 in. W.C.	0.037 to 0.040 in.	0.38 gal/hr per 100k
Smoker cabinet	11 in. W.C.	0.051 to 0.055 in.	7.2 CFH at 18k
Three grill burners	11 in. W.C.	0.041 to 0.043 in.	4.8 CFH each
RV furnace	10.5 in. W.C.	0.065 to 0.068 in.	1.39 lb/hr total
Patio heater	11 in. W.C.	0.076 to 0.081 in.	0.44 gal/hr total
Turkey fryer	11 in. W.C.	0.088 to 0.090 in.	22 CFH at 55k
Fire pit ring	11 in. W.C.	0.096 to 0.100 in.	0.71 gal/hr total
Forge burner pair	11 in. W.C.	0.101 to 0.104 in.	20 CFH each

💡Calculation Tips

Use per-burner demand, not total nameplate.

A 36,000 BTU grill with three burners needs each orifice sized for about one-third of the load before you add any design margin.

Compare exact diameter to the nearest drill bit.

The closest numbered drill may deliver a little more or less BTU than the ideal hole, so the variance output helps you see the likely shift.

Propane orifice sizing are the process of determining the proper diameter of a brass orifice given the heat output requirement of the appliance and the propane pressure. The orifice is a small hole in the manifold that controls the amount of propane that exit the appliance into the burner tube. If the orifice size is too small for the BTU output requirements of the appliance, then the propane will not be able to supply enough heat to the appliance.

If the orifice size is too large, then there will be a waste of propane gas as it will exit the appliance without being fully combust. Ensuring that the propane orifice size is set to the correct diameter will ensure that there is a proper flow of propane to create a blue flame. In order to size the orifice for propane appliances, you must first determine the total heat load of the appliance.

How to Size Propane Orifices

The total heat load is measured in British thermal unit (BTUs) per hour. To calculate the BTUs required for each burner, you can divide the total BTUs by the number of burners that the appliance include. For propane appliances, the heating value of propane is approximately 2,500 BTUs per cubic foot of vaporized propane.

Additionally, the calculation of the size of the orifices must account for the pressure of the propane within the appliance. The standard propane pressure for appliances is 11 inch of water column. However, this standard may change with the output of the regulator on the propane tank or the altitude of the propane tank.

In order to size the orifices for propane appliances, many people use printed charts that show the sizes of drill bits for the orifices of different BTU output. These charts typically list BTU output for drill bits numbered #70, #44, and others. For example, a #56 drill bit may output 15,000 BTUs per hour, while a #44 drill bit may output 51,600 BTUs per hour.

These charts are printed with the assumption that the propane pressure within the appliance is 11 inches of water column, or standard propane pressure. Should the propane pressure within the appliance be lower than the standard 11 inches of water column, then the BTU output of the appliance will be lower than the BTU rating printed on these charts. As such, the calculations for propane orifices must be adjustable based off the actual propane pressure within the appliance.

For propane orifices to be sized correctly, you must measure the propane pressure within the appliance. A manometer can be used to determine the propane pressure within the test port of the propane manifold. The gauge that reads the propane pressure within the propane tank isnt an accurate gauge of the propane pressure within the appliance.

The regulator that is included with the propane tank is what sets the propane pressure within the appliance. In cold climate, a design margin of propane capacity of 10% may need to be provided for the design of propane appliances. As the temperature within the area where the appliance is to be used is lower, the propane will vaporize at a slower rate.

This extra 10% of propane capacity is provided to ensure that the appliance will have an adequate supply of propane even in cold climates. In order to drill propane orifices, you must use brass tubing. Brass tubing is the best material for the orifices in propane appliances due to its durability.

To drill the orifices, you can use the numbered twist bits as they allow for precision in thousandths of an inch. Once you have drilled the orifices, the fire must be tested to ensure that the orifices are of the proper size. If the appliance flame is of a steady blue color, the orifices are sized correctly.

If the flame has yellow tips, the orifices are too small for the propane pressure. If the flame lift away from the burner tubes, then the orifices are too large for the propane pressure. The requirements of different appliances will vary in the sizing of the orifices for the propane gas.

Appliances that require low BTUs, such as smokers, may have only one orifice providing 18,000 BTUs per hour. Fire pits, however, may have many large orifices to allow for a large ring of flame to exit the appliance. Areas with high altitudes have thinner air; thus, the propane pressure may be lower in these areas.

Additionally, each orifice in a propane manifold must be the same size to allow for even heat distribution from each burner of the appliance. In order to properly size the propane orifices, there are some mistakes that must be avoided. For example, failing to divide the total BTUs by the number of burners will result in undersized orifices.

Another example of a common mistake is to ignore the discharge coefficient. The discharge coefficient accounts for imperfections in the orifices. Any rough edge to the orifices will lower the coefficient and the BTUs that will exit the appliance.

Additionally, another mistake to avoid is failing to ensure that the area is well ventilated. Since propane gas is heavier than air, it can pool in low areas if there is a propane leak. Properly sizing the propane orifices will ensure that propane gas will exit the appliance at the proper rate to provide heat to the appliances according to the propane pressure.