CFH to BTU Calculator: Convert Cubic Feet of Gas

This calculator converts a flow rate of natural gas or propane from cubic feet per hour (CFH) to British thermal units per hour (BTU/h). You enter the gas flow in CFH and select the gas type (natural gas or propane); the calculator returns the equivalent heating value in BTU per hour. The conversion uses the standard heating value of each gas, which is the amount of heat released when a cubic foot of that gas is completely burned.

Formula

The conversion is a simple multiplication:

BTU/h = CFH × Heating Value (BTU per cubic foot)

Where:

• CFH = flow rate of gas in cubic feet per hour (ft³/h)
• Heating Value = the average heat content of one cubic foot of the gas, in BTU/ft³. For natural gas, this is approximately 1,000 BTU/ft³; for propane, approximately 2,500 BTU/ft³.

These heating values are industry-standard approximations. The actual heating value of natural gas varies by region and composition, typically between 950 and 1,100 BTU/ft³. Propane is more consistent, but can vary slightly with temperature and pressure.

Worked Example

Using the calculator defaults: you have a gas flow of 100 CFH of natural gas.

1. Identify the heating value: natural gas = 1,000 BTU/ft³.
2. Multiply the flow by the heating value: 100 CFH × 1,000 BTU/ft³ = 100,000 BTU/h.
3. The calculator shows 100,000 BTU/h.

If you switch to propane at the same flow: 100 CFH × 2,500 BTU/ft³ = 250,000 BTU/h.

Why Convert CFH to BTU?

Gas appliances are rated in BTU/h (or BTU/hr) to indicate their heat output. But gas meters and piping systems measure flow in cubic feet per hour. To size a gas line, a regulator, or a meter for a new appliance, you need to know whether the pipe can deliver enough BTU to feed the appliance. Conversely, if you have a gas meter that reads in CFH, you can estimate the total BTU load of all connected appliances to see if it matches the meter’s capacity.

This conversion is also used when comparing the cost of different fuels: if you know the price per cubic foot of gas and the BTU content, you can calculate the cost per BTU and compare with electricity or oil.

How to Use the Calculator

Enter the gas flow in cubic feet per hour (CFH). This number is usually found on the gas meter (often labeled in ft³ or m³) or on the appliance’s nameplate. Then choose the gas type. The calculator multiplies the flow by the heating value and gives you the BTU/h output.

If you have a gas flow in cubic meters per hour (m³/h), convert to CFH first by multiplying by 35.3147 (1 m³ = 35.3147 ft³). For example, 10 m³/h × 35.3147 = 353.147 CFH.

Common Mistakes and Misconceptions

One common error is using the heating value of the gas at standard conditions versus actual conditions. The heating value used here (1,000 BTU/ft³ for natural gas) is for gas at standard temperature and pressure (usually 60°F and 1 atmosphere). If the gas is compressed or at a different temperature, the actual heat content per cubic foot changes, but for most residential and commercial applications the standard value is accurate enough.

Another mistake is confusing CFH with CCF (hundred cubic feet) or MCF (thousand cubic feet). Gas bills often use CCF (100 ft³) or MCF (1,000 ft³). To use this calculator, convert CCF to CFH by multiplying by 100, and MCF to CFH by multiplying by 1,000. For example, a meter reading of 5 CCF per hour is 500 CFH.

Also, don’t confuse BTU/h with BTU (which is a unit of energy, not power). BTU/h is a rate; BTU is a total amount. The calculator gives you the rate of energy production.

Limitations of the Formula

The formula assumes complete combustion and that the gas is at standard conditions. Real-world efficiency of a burner or appliance is typically 70–95%, so the actual heat delivered to your home will be less than the calculated BTU/h. For example, a furnace rated at 100,000 BTU/h input might deliver only 80,000 BTU/h of heat to your rooms if it is 80% efficient.

The heating value of natural gas also varies by source. If you need a precise number, check with your gas utility for the specific heating value (often called the “higher heating value� or HHV) of the gas they deliver. The calculator uses the HHV, which includes the heat from condensing water vapor; some applications use the lower heating value (LHV), which excludes that heat.

When to Use This Conversion

Use this calculator when you need to:

• Size a gas line or pipe for a new appliance. Local codes often require a minimum pipe diameter based on the total BTU/h load.
• Check if your existing gas meter can handle an additional appliance. Meters are rated in CFH, but appliance ratings are in BTU/h.
• Convert gas flow readings from a meter to BTU for energy audits or cost calculations.
• Compare the heating capacity of gas appliances with electric ones (1 kW = 3,412 BTU/h).

For example, a typical gas range uses about 65,000 BTU/h when all burners are on high. At 1,000 BTU/ft³, that requires 65 CFH of natural gas. A standard residential gas meter can often supply 200–300 CFH, so it would be fine.

Safety and Accuracy Notes

Always consult a licensed professional before modifying gas piping, installing appliances, or adjusting gas pressures. Incorrect assumptions about gas flow can lead to under-sized pipes, which can cause low pressure, incomplete combustion, and carbon monoxide production. Use the heating value provided by your gas supplier for critical applications. For propane, the heating value can vary slightly with temperature; the 2,500 BTU/ft³ figure is a common average.

Frequently Asked Questions

What is CFH? CFH stands for cubic feet per hour, a unit of volumetric flow rate. It measures how many cubic feet of gas pass a point in one hour.

What is BTU? BTU (British thermal unit) is a unit of energy. One BTU is the amount of heat needed to raise one pound of water by one degree Fahrenheit. BTU/h is a unit of power (energy per hour).

How many BTU are in a cubic foot of natural gas? Approximately 1,000 BTU per cubic foot at standard conditions. This is the average for natural gas; the exact value is usually between 950 and 1,100 BTU/ft³ depending on the gas composition.

How many BTU are in a gallon of propane? A gallon of propane contains about 91,500 BTU. This is a different conversion because propane is often measured by volume in gallons (liquid) rather than as a gas in cubic feet. When vaporized, one cubic foot of propane gas contains about 2,500 BTU.

Can I convert CFH to kW? Yes, but you need to go through BTU first. 1 kW = 3,412 BTU/h. So divide the BTU/h result by 3,412 to get kilowatts. For example, 100,000 BTU/h ÷ 3,412 = 29.3 kW.

Why does the calculator ask for gas type? Because natural gas and propane have different energy densities per cubic foot. Propane has a higher heating value (about 2,500 BTU/ft³) than natural gas (about 1,000 BTU/ft³), so the same flow in CFH produces more BTU with propane.

Related

• Btu Gas Calculator: How to Size a Heater
• BTU to kWh Calculator: Convert Heat Units
• BTU Load Calculator: What It Means & How to Use It

in cfh | Gas flow | CFH | 100 | 0
sel gas | Gas type | Natural gas=1000, Propane=2500 | 1000
out btu | Heat output | BTU/h | cfh * gas | 0