1. Heating value (calorific value)
   Heat released by complete combustion of a unit mass (or volume) of fuel.

• Solid/liquid: MJ/kg
• Gas: MJ/m^3 (usually at standard conditions)

2. Standard fuel (standard coal)
   Engineering conversions often use "standard coal equivalent." In China the LHV of standard coal is commonly:

• $Q_{ce} = 29.3076\ \text{MJ/kg}$ (i.e., $7000\ \text{kcal/kg}$)

Conversion factor (standard coal equivalent for fuel $i$):

• $b_{ce} = \dfrac{Q_i}{Q_{ce}}$ (more common when using LHV)

3. Heat equivalent
   Heat associated with a given amount of fuel or its equivalence to standard fuel. For fuel mass $m$ and LHV $Q_{LHV}$:

• Heat released: $Q = m\cdot Q_{LHV}$
• Standard coal equivalent: $m_{ce} = \dfrac{m\cdot Q_{LHV}}{Q_{ce}}$