Heat Energy Calculator (Q = mcΔT)
Calculate the heat energy needed to change a substance's temperature. Enter the mass, the material's specific heat capacity, and the temperature change, and this calculator applies Q = mcΔT to give the energy in joules.
Formula
Q = m × c × ΔT
- Q is the heat energy (joules) needed to change a substance's temperature.
- m is mass (kg), c is specific heat capacity (J/kg·K), and ΔT is the temperature change.
- A temperature change of 1 K equals a change of 1 °C, so either unit works for ΔT.
- Specific heat varies by material: water ≈ 4186, aluminium ≈ 900, iron ≈ 450 J/kg·K.
- A positive ΔT means heating (energy in); a negative ΔT means cooling (energy out).
- This assumes no phase change — melting or boiling needs latent heat, which Q = mcΔT doesn't cover.
Heating 1 kg of water by 10 °C
Inputs
- Mass: 1 kg
- Specific Heat Capacity: 4186 J/kg·K
- Temperature Change: 10 K (or °C)
Q = 1 kg × 4186 J/kg·K × 10 K = 41,860 J (about 41.9 kJ) to raise the water's temperature by 10 °C.
Frequently asked questions
What does Q = mcΔT calculate?
It gives the heat energy required to change a substance's temperature, based on its mass, specific heat capacity, and the size of the temperature change.
What is specific heat capacity?
It's the energy needed to raise 1 kg of a material by 1 K. Water's is high (≈4186 J/kg·K), which is why it heats and cools slowly compared with metals.
Do I use Kelvin or Celsius for ΔT?
Either — a change of 1 K is the same size as a change of 1 °C. Only the temperature difference matters, not the absolute scale.
Does this include melting or boiling?
No. Q = mcΔT covers temperature change only. Phase changes (solid↔liquid↔gas) require latent heat, calculated separately.