Heat converters
Fuel Efficiency - Volume Converter
Convert J/m³, BTU/ft³, kWh/m³ and other energy-per-volume units.
Result
37.2589 MJ/m³
1000 BTU/ft³ = 37.2589 MJ/m³
Volume-per-energy units are reciprocals of energy-per-volume units, so they convert through 1 ÷ value and a zero entry shows a dash.
All units for this value
| Unit | Symbol | Value |
|---|---|---|
| Joule per cubic meter | J/m³ | 37258900 |
| Kilojoule per cubic meter | kJ/m³ | 37258.9 |
| Megajoule per cubic meter | MJ/m³ | 37.2589 |
| Joule per liter | J/L | 37258.9 |
| Kilojoule per liter | kJ/L | 37.2589 |
| Kilocalorie (IT) per cubic meter | kcal/m³ | 8899.15 |
| Kilocalorie (IT) per liter | kcal/L | 8.89915 |
| Watt-hour per cubic meter | Wh/m³ | 10349.7 |
| Kilowatt-hour per cubic meter | kWh/m³ | 10.3497 |
| Kilowatt-hour per liter | kWh/L | 0.0103497 |
| BTU (IT) per cubic foot | BTU/ft³ | 1000 |
| BTU (IT) per US gallon | BTU/gal | 133.681 |
| Therm per US gallon | thm/gal | 0.00133712 |
| Cubic meter per joule | m³/J | 2.68392e-8 |
| Liter per kilowatt-hour | L/kWh | 96.6211 |
About this calculator
Fuel efficiency by volume expresses how much energy is packed into each unit of fuel volume, using units like joules per cubic metre, BTU per cubic foot, and kilowatt-hours per cubic metre. This converter is useful for comparing gaseous and liquid fuels that are metered and sold by volume, such as natural gas, propane, and heating oil.
How it works in plain English
Energy-per-volume units all describe the same underlying idea — how much energy is contained in a given volume of fuel — so the converter anchors every conversion through joules per cubic metre. It multiplies your entered value by a factor to reach that anchor, then divides by a second factor to reach your chosen target unit, whether that's a metric SI unit, a calorie-based unit, an electrical kilowatt-hour unit, or a US customary BTU-based unit.
The converter also includes the reciprocal family of units, volume-per-energy units such as cubic metres per joule or litres per kilowatt-hour, which describe how much fuel volume is needed to produce one unit of energy rather than how much energy a given volume produces. Moving into or out of these reciprocal units means dividing one by the value instead of multiplying by a fixed factor, since a larger energy-per-volume figure corresponds to a smaller volume-per-energy figure. Because dividing by zero has no answer, entering zero into a reciprocal-unit field shows a dash instead of a number, since zero volume or zero energy has no meaningful reciprocal efficiency.
Choose your source and target units from the from and to menus, type in a value, and the result appears immediately alongside a full table listing that figure in every supported unit. A precision control adjusts the number of decimal places shown, and a swap button reverses the two selected units instantly.
The formula
- value_in_target = value_in_source × (source factor to J/m³) ÷ (target factor to J/m³)
- 1 BTU (IT)/ft³ = 37,258.9457 J/m³
- 1 kWh/m³ = 3,600,000 J/m³
- 1 kcal (IT)/m³ = 4,186.8 J/m³
- Reciprocal units (e.g. m³/J, L/kWh): value_in_target = 1 ÷ (value_in_source × factor); zero has no reciprocal
Worked example
Suppose a natural gas supplier lists an energy content of 1,030 BTU/ft³ and you want that figure in MJ/m³. First convert to joules per cubic metre: 1,030 × 37,258.9457 = 38,376,713.6 J/m³. Then divide by 1,000,000 to reach megajoules per cubic metre: 38,376,713.6 ÷ 1,000,000 ≈ 38.38 MJ/m³.
Entering 1,030 into the BTU/ft³ field with MJ/m³ selected as the target shows about 38.38 MJ/m³ immediately. The full unit table also shows this same gas equals roughly 10.66 kWh/m³ and about 9,166 kcal/m³, all worked out from that one entered value.
Fuel efficiency by volume unit equivalents
| Unit | Equal to (J/m³) |
|---|---|
| 1 J/m³ | 1 |
| 1 kJ/m³ | 1,000 |
| 1 MJ/m³ | 1,000,000 |
| 1 J/L | 1,000 |
| 1 kcal (IT)/m³ | 4,186.8 |
| 1 kcal (IT)/L | 4,186,800 |
| 1 Wh/m³ | 3,600 |
| 1 kWh/m³ | 3,600,000 |
| 1 BTU (IT)/ft³ | 37,258.9457 |
| 1 BTU (IT)/US gal | 278,716.3 |
Standard energy and volume unit definitions
Frequently asked questions
Why is natural gas measured in BTU per cubic foot?
Natural gas is metered and billed by volume, so its energy content is naturally expressed per unit of volume rather than per unit of mass. BTU per cubic foot has long been the standard unit in the US gas industry, while many other countries use megajoules per cubic metre or kilowatt-hours per cubic metre for the same purpose, all of which this converter handles.
What does litres per kilowatt-hour actually describe?
It's a reciprocal, volume-per-energy unit describing how much fuel volume, in litres, is needed to produce one kilowatt-hour of energy. A smaller number means a more energy-dense fuel, since less volume is needed for the same energy output, which is the opposite relationship from the direct energy-per-volume units like kWh/m³.
Why does zero show as a dash for some units here?
Reciprocal units such as cubic metres per joule are calculated by dividing one by the entered value, and dividing by zero has no defined mathematical result. Since zero volume or zero energy also doesn't correspond to a real fuel efficiency figure, the converter displays a dash rather than zero or an error message.
How do I compare natural gas to heating oil, which is measured differently?
As long as both fuels' energy contents are known on a volume basis, such as BTU per cubic foot for gas and BTU per US gallon for oil, this converter can bring both to a common unit like MJ/m³ or kWh/m³ for a direct side-by-side comparison, without needing any separate density information.
Is the therm-per-gallon unit here the same therm used on gas bills?
Yes, it uses the same International Table-based BTU definition that underlies the therm used in gas billing, where one therm equals 100,000 BTU. It's included alongside BTU-per-gallon for liquid fuels priced or measured that way, converting through the same joule-per-cubic-metre anchor as every other unit in this tool.
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