BTU/hr to CFH Converter — Natural Gas & Propane
Convert an appliance load from BTU/hr to CFH (cubic feet per hour) — the flow unit gas pipe capacity tables use.
Calculator
100,000 BTU/hr is about 100.0 CFH on natural gas (~1000 BTU/cu ft) or 39.7 CFH on propane (~2516 BTU/cu ft). CFH (cubic feet per hour) is what gas-pipe capacity tables use. ⚠️ Gas work is for licensed professionals only.
Gas-pipe capacity tables are written in CFH — cubic feet of gas per hour — but appliance ratings come in BTU/hr. To move between them you divide by the fuel's heating value: how many BTU are packed into each cubic foot. Natural gas holds roughly 1000 BTU per cubic foot; propane (LP) is denser at about 2516 BTU per cubic foot, so the same BTU load is far fewer cubic feet on propane.
This converter shows both fuels at once so you can see the difference. It is a pure unit conversion — no design assumptions — which makes it handy any time you are cross-checking a sizing chart or a meter rating.
Formula
The conversion is one division:
CFH = BTU/hr ÷ heating value
- Natural gas: heating value ≈ 1000 BTU per cubic foot
- Propane / LP: heating value ≈ 2516 BTU per cubic foot
To go the other way, multiply: BTU/hr = CFH × heating value.
Worked example
Take a 100,000 BTU/hr appliance:
- Natural gas: 100,000 ÷ 1000 = 100 CFH
- Propane: 100,000 ÷ 2516 ≈ 39.7 CFH
Same appliance, same BTU, but propane is only about 40 CFH because each cubic foot carries more energy. That is why natural-gas and propane pipe-capacity tables look so different.
Heating values, therms and meter ratings
Heating values are nominal industry figures and vary slightly with gas composition, altitude and temperature — utilities publish a local "therm factor," and 1 therm equals 100,000 BTU. For sizing work the round 1000 and 2516 values are the standard planning conventions and are what the code tables assume. If you need extreme precision (large commercial metering, for instance), use your utility's stated heating value.
CFH is also how gas meters are rated: a meter stamped with a maximum CFH tells you the largest total load it can serve. If your connected load in CFH approaches the meter rating, the utility may need to upsize the meter — another reason to know your load in CFH, not just BTU.
Frequently asked questions
How do I convert BTU to CFH?
Divide the BTU/hr by the fuel's heating value: 1000 for natural gas or 2516 for propane. So 100,000 BTU/hr is 100 CFH on natural gas or about 39.7 CFH on propane.
Why is propane fewer CFH than natural gas?
Because propane is more energy-dense — about 2516 BTU per cubic foot versus roughly 1000 for natural gas. The same BTU load is fewer cubic feet, so propane systems move less volume for the same heat.
What is a therm?
A therm is 100,000 BTU — a billing unit on your gas statement. At about 1000 BTU per cubic foot, one therm of natural gas is roughly 100 cubic feet. It does not change the CFH conversion; it is just how the utility measures energy sold.
Do I use CFH to size gas pipe?
Yes. Pipe-capacity tables (including the NFPA-54 longest-length method) list capacity in CFH, so you convert your BTU load to CFH first. The gas pipe size tool does both steps together.