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BIPM-ratified constants · v1.0

Converter

Btu, to cfh converter calculator.

Convert BTU/hr to cubic feet per hour (CFH) using fuel heating value. Supports natural gas, propane, butane, and custom fuels.

From

natural gas

natural_gas

1000 natural_gas =100Cubic Feet per Hour

Equivalents

Precision: 6 dp · Notation: Decimal · 5 units

1,000 BTU/ft³

Natural Gasnatural_gas100

2,516 BTU/ft³

Propanepropane39.7456

3,200 BTU/ft³

Butanebutane31.25

1,011 BTU/ft³

Methanemethane98.912

Heating Value

Customcustom100

Common pairings

1 natural_gasequals39.7456 propane
1 natural_gasequals31.25 butane
1 natural_gasequals98.912 methane
1 propaneequals100 natural_gas
1 propaneequals31.25 butane
1 propaneequals98.912 methane
1 butaneequals100 natural_gas
1 butaneequals39.7456 propane

The conversion

How the value
is computed.

BTU to CFH Converter: Formula, Variables, and Applications

Converting British Thermal Units per hour (BTU/hr) to cubic feet per hour (CFH) is a fundamental calculation in gas system design, appliance installation, and pipe sizing. The conversion bridges the gap between an appliance's energy demand — expressed in BTU/hr — and the volumetric gas flow rate that supply infrastructure must deliver.

The Core Conversion Formula

The BTU to CFH formula is straightforward:

CFH = BTU/hr ÷ HV

Where each variable represents:

  • CFH — Cubic Feet per Hour: the volumetric flow rate of gas required by the appliance
  • BTU/hr — British Thermal Units per Hour: the rated heat input of the gas appliance
  • HV — Heating Value: the energy content of the fuel in BTU per cubic foot

Heating Values by Fuel Type

The heating value is the single most important variable in this calculation. Different fuels release different amounts of energy per cubic foot of gas burned. Standard reference values used in engineering practice include:

  • Natural Gas: approximately 1,020 BTU per cubic foot (range: 950–1,150 BTU/cu ft depending on pipeline composition)
  • Propane (LP Gas): approximately 2,516 BTU per cubic foot
  • Butane: approximately 3,262 BTU per cubic foot

The U.S. Energy Information Administration (EIA) Energy Conversion Calculators provides standardized heating values recognized across the energy industry. For non-standard blends or specialty fuels, a custom heating value obtained from gas analysis data should be used instead of a generic default.

Why Gas Pipe Sizing Requires CFH

Gas utilities, engineers, and plumbers measure gas delivery capacity in cubic feet per hour, not BTU per hour. Pipe sizing charts, regulator ratings, and gas meter capacities are all expressed in CFH. According to the El Dorado County Gas Pipe Line Calculation Sizing reference, determining the correct pipe diameter requires totaling the CFH demand of all connected appliances and then selecting pipe diameter from pressure-drop tables. Without the BTU to CFH conversion, accurate pipe sizing is impossible.

Step-by-Step Calculation Examples

Example 1 — Natural Gas Furnace: A residential furnace is rated at 80,000 BTU/hr. Using a heating value of 1,020 BTU/cu ft for natural gas:

  • CFH = 80,000 ÷ 1,020 = 78.43 CFH

Example 2 — Propane Water Heater: A tankless water heater is rated at 199,000 BTU/hr running on propane (HV = 2,516 BTU/cu ft):

  • CFH = 199,000 ÷ 2,516 = 79.09 CFH

Notice that despite the higher BTU rating, the propane appliance requires nearly the same volumetric flow as the natural gas furnace — because propane contains more than twice the energy per cubic foot. This demonstrates why fuel type cannot be ignored in the conversion.

Real-World Applications

  • Gas Pipe Sizing: Plumbers and mechanical engineers total CFH loads for all appliances on a gas line to select the correct pipe diameter and avoid pressure drops that cause burner malfunction.
  • Meter Sizing: Gas utility meters carry a maximum CFH rating. Converting appliance loads to CFH confirms the meter can serve peak simultaneous demand.
  • Fuel Conversion Projects: When switching from propane to natural gas, the CFH requirement changes because the heating value drops from 2,516 to roughly 1,020 BTU/cu ft. The Auburn University Extension guide on Converting to Natural Gas explains how this shift affects burner orifice sizing, gas pressure regulation, and overall system design.
  • Combustion Air Design: Adequate combustion air supply is proportional to fuel consumption rate in CFH, making this conversion critical for boiler room and furnace room ventilation sizing.
  • Energy Auditing: Comparing rated CFH against measured gas meter readings helps auditors identify combustion inefficiencies or appliance degradation over time.

HHV vs. LHV: An Important Distinction

Gas appliance ratings and utility billing typically reference the higher heating value (HHV), which includes the latent heat of water vapor in combustion products. The lower heating value (LHV) excludes that latent heat and yields a slightly lower number. Using LHV when HHV is expected — or vice versa — can produce CFH errors of 5–10%, which may result in undersized piping or overloaded meters. Always confirm which heating value basis applies to the appliance nameplate data before performing the conversion.

Reference

Frequently asked questions

What is a BTU to CFH converter used for?
A BTU to CFH converter translates an appliance's heat input rating (in BTU per hour) into the volumetric gas flow rate (in cubic feet per hour) required to sustain that output. Gas engineers, plumbers, and HVAC technicians rely on this conversion to size gas supply pipes, select meter capacities, verify regulator ratings, and confirm that a fuel supply system can meet the combined demand of all connected appliances under peak operating conditions.
What heating value should be used for natural gas in a BTU to CFH calculation?
Natural gas typically carries a heating value of approximately 1,020 BTU per cubic foot, though pipeline composition causes this figure to range from roughly 950 to 1,150 BTU/cu ft depending on region and season. The U.S. Energy Information Administration uses 1,020 BTU/cu ft as the standard reference value. For critical sizing work, request the actual BTU/cu ft value from the local gas utility, since deviations from the standard affect CFH results and downstream pipe sizing decisions.
How do you convert 100,000 BTU/hr to CFH for natural gas?
Divide the BTU/hr rating by the heating value of natural gas. Using the standard value of 1,020 BTU per cubic foot: CFH = 100,000 ÷ 1,020 = 98.04 cubic feet per hour. This means a 100,000 BTU/hr appliance — such as a mid-sized residential furnace or commercial water heater — consumes just under 100 cubic feet of natural gas per hour at full rated input.
Why does the fuel type change the CFH result for the same BTU/hr rating?
Different fuels contain vastly different amounts of energy per cubic foot. Propane holds about 2,516 BTU/cu ft while natural gas holds about 1,020 BTU/cu ft. A 50,000 BTU/hr burner running on natural gas requires 49.02 CFH, but the same burner converted to propane needs only 19.87 CFH. When switching fuels, the CFH demand changes significantly even though the appliance BTU rating stays the same, which is why fuel conversion projects require new pipe sizing and orifice adjustments.
What is the difference between BTU/hr and CFH in gas systems?
BTU per hour measures the rate of heat energy output or input — it describes the thermal performance of an appliance. Cubic feet per hour measures the volumetric flow rate of gas passing through a pipe or meter — it describes physical gas movement. Gas infrastructure (pipes, meters, regulators) is rated in CFH because it moves gas by volume. Appliances are rated in BTU/hr because they perform thermal work. The BTU to CFH conversion links these two measurement systems, allowing engineers to match appliance demand to physical supply capacity.
Can the BTU to CFH formula be used for commercial and industrial gas systems?
Yes. The formula CFH = BTU/hr ÷ HV applies equally to residential, commercial, and industrial gas systems. For large-scale applications such as industrial boilers, kilns, or commercial kitchen equipment with ratings in the millions of BTU/hr, the same arithmetic applies — only the scale changes. Industrial users often work with custom heating values derived from onsite gas chromatography data rather than standard reference figures, since pipeline gas composition at industrial facilities can differ meaningfully from residential supply standards.