How to convert cubic feet to btu
Natural gas is sold by both energy content (BTU, therms, MJ) and volume (cubic feet, cubic meters). For typical US pipeline gas, 1 ft³ ≈ 1,037 BTU. The factor varies a few percent up or down depending on gas composition; utilities publish their current value monthly.
BTU = ft³ × ~1,037
Worked examples
Example 1: 100 ft³ of natural gas
100 × 1,037 = 103,700 BTU, or about 1.04 therms.
Example 2: 1 therm of natural gas
100,000 ÷ 1,037 ≈ 96.4 ft³.
Example 3: 1 hour of a 100,000 BTU/hr furnace
100,000 ÷ 1,037 ≈ 96.4 ft³ of gas burned per hour at 100% efficiency.
| Cubic feet of natural gas → energy | Conversion factor | Worked example |
|---|---|---|
| 1 ft³ | × 1,037 | 1,037 BTU |
| 10 ft³ | × 1,037 | 10,370 BTU |
| 100 ft³ (1 CCF) | × 1,037 | 103,700 BTU |
| 1,000 ft³ (1 MCF) | × 1,037 | 1.037 million BTU |
Common uses
- Reading natural gas utility bills (CCF or MCF on the meter)
- Sizing furnaces, boilers, and water heaters
- Estimating heating cost per BTU
- Comparing natural gas to propane, oil, or electricity by BTU equivalent
Where this conversion comes up
Cubic feet of natural gas converts to BTU because gas is sold by volume but billed by energy content. The factor varies a few percent by gas composition and pressure.
- Sizing a sauna heater or other gas appliance against utility billing.
- Greenhouse heating — converting volume of propane or natural gas burned to BTU output.
- Comparing fuel options for HVAC sizing — see the HVAC airflow calculator for the volume side.
Common mistakes to avoid
- Mixing natural gas with propane. 1 ft³ of natural gas ≈ 1,037 BTU; 1 ft³ of propane vapor ≈ 2,516 BTU. Confirm fuel type before converting.
- Confusing standard cubic feet (SCF) with actual cubic feet.Utilities measure gas at standard temperature and pressure. Volume at higher temperature is more.
- Forgetting that BTU is energy, not power. BTU/hr is the rate; BTU is the total. A 100,000 BTU/hr furnace burns about 96 ft³ of natural gas per hour at full output.
Expert tips
- Multiply cubic feet of natural gas by 1,037 to get BTU. This is the EIA-published US average. Local heating value can vary ±2%, but 1,037 is the right working number for residential utility billing.
- For propane, use 2,516 BTU per cubic foot of vapor. Propane has roughly 2.5× the BTU per cubic foot as natural gas because the molecules are larger.
- For utility bills, MMBTU = 1,000,000 BTU = ~964 ft³ of natural gas.MMBTU is the standard unit on commercial gas bills. See the sauna heater calculator for a practical heat-load example.
- For heating-system sizing, BTU is the design unit. A typical home needs 30–60 BTU/hr per cubic foot of conditioned space, depending on insulation. See the HVAC airflow calculator.