Heat Density Converter
ScienceConvert heat (energy) density between joules per cubic metre, BTU per cubic foot, and calories per cubic centimetre — used for fuel and thermal storage.
From
To
All conversionsfor 1 BTU per Cubic Foot (BTU/ft³)
| Joules per Cubic Metre (J/m³) | 37259.1 |
| Kilojoules per Cubic Metre (kJ/m³) | 37.2591 |
| BTU per Cubic Foot (BTU/ft³) | 1 |
| Calories per Cubic Centimetre (cal/cm³) | 0.0089051386 |
What is a Heat Density?
The Heat Density Converter converts thermal (heat) energy density between joules per cubic metre (SI), BTU per cubic foot (imperial), and calories per cubic centimetre (CGS). Heat density measures how much thermal energy is contained or released per unit volume — a key quantity for comparing fuels, thermal storage media, and combustion processes on a per-volume basis.
Enter a value in any supported unit and the converter calculates the equivalent instantly. For the related per-mass quantity, see the Specific Heat Capacity Converter, and for natural gas-specific conversions, see the Natural Gas Unit Converter.
How to use this Heat Density calculator
- Choose your starting unit from the source dropdown — for example, "BTU per Cubic Foot (BTU/ft³)".
- Enter the numeric value you want to convert in the input field.
- Choose your target unit from the destination dropdown — for example, "Joules per Cubic Metre (J/m³)".
- Read the converted result, which updates instantly as you type or change units.
- Use the swap (⇅) button if you need to reverse the conversion direction.
- Use the copy button to grab the result for a fuel comparison or thermal storage calculation.
Formula & Methodology
The converter's base unit is joules per cubic metre (J/m³). Every supported unit has a fixed multiplier: - 1 kilojoule per cubic metre (kJ/m³) = 1,000 J/m³ - 1 BTU per cubic foot (BTU/ft³) ≈ 37,259.1 J/m³ - 1 calorie per cubic centimetre (cal/cm³) = 4,184,000 J/m³ Any conversion follows: Result = Input × (toBase of source unit ÷ toBase of target unit) Worked example — converting natural gas's typical heat density of 1,000 BTU/ft³ to J/m³ (via kJ/m³): Result = 1,000 × 37,259.1 = 37,259,100 J/m³ = 37.26 MJ/m³ This matches the commonly cited heating value for natural gas expressed in metric units.
Frequently Asked Questions
Heat density (also called volumetric energy or heat content) measures the amount of thermal energy contained or released per unit volume of a substance — useful for comparing fuels, thermal storage media, or combustion processes on a per-volume basis rather than per-mass.
Multiply the BTU/ft³ value by 37,259.1, since one BTU per cubic foot equals approximately 37,259.1 joules per cubic metre. Enter your value with 'BTU per Cubic Foot (BTU/ft³)' as the source and 'Joules per Cubic Metre (J/m³)' as the target to apply this automatically.
Natural gas heating value is often expressed as energy per unit volume (like BTU per cubic foot), which is a form of heat density — this is the same underlying concept used when converting between therms, BTU, and cubic feet of natural gas. See the [Natural Gas Unit Converter](/natural-gas-converter/) for gas-specific unit conversions.
Comparing fuels by heat density (energy per unit volume) is especially relevant for gaseous and liquid fuels where storage tank size matters, since a fuel with higher heat density delivers more energy for the same storage volume — useful when comparing options like natural gas, propane, or hydrogen for a given application.
Heat density measures energy content per unit volume (J/m³), while [specific heat capacity](/specific-heat-capacity-converter/) measures the energy needed to raise a unit mass by one degree (J/kg·K) — they describe different things: heat density is about stored or released energy, specific heat capacity is about temperature response to added energy.
Multiply the cal/cm³ value by 4,184,000, since one calorie per cubic centimetre equals 4,184,000 joules per cubic metre — this large multiplier reflects the substantial unit scale difference between cubic centimetres and cubic metres (a factor of one million) combined with the calorie-to-joule conversion.
Natural gas has a heat density of roughly 37 to 39 MJ/m³ (about 1,000 to 1,050 BTU/ft³), while denser fuels like propane or liquid fuels have substantially higher heat density per unit volume, reflecting their more compact energy storage.
Calorific value (or heating value) is often expressed as heat density (energy per unit volume) for gases, or as specific energy (energy per unit mass) for solid and liquid fuels — the terms overlap but aren't strictly identical, since calorific value can be reported either way depending on the fuel type and industry convention.
Energy engineers comparing fuel options across different unit systems, thermal storage designers calculating tank or reservoir sizing, and combustion engineers working with international equipment specifications all commonly need accurate heat density conversions.
Yes, particularly for gaseous fuels — the same mass of gas occupies a different volume at different temperatures and pressures, so heat density figures are typically quoted at standard reference conditions, and comparisons should use figures measured under the same conditions.
Also known as