Every material resists a change in temperature to some degree. Pour the same amount of heat into a kilogram of water and a kilogram of copper and the copper warms up roughly forty times as much. Specific heat capacity is the number that captures that difference — the energy it takes to lift one kilogram of a substance by one degree Celsius. This calculation shows up in engineering (sizing heaters and coolers), cooking, climate science, and any problem where something has to be warmed or chilled.
The specific heat formula
Worked example
The calculator’s defaults are 2 kg of water, a specific heat of 4184 J/(kg·°C), and a temperature change of 25°C.
Energy for a single degree first:
Then across the full 25 degrees:
That’s about 209 kJ, or 0.058 kWh — a useful reality check on why an electric kettle takes a couple of minutes and a fair chunk of a power bill’s worth of energy to boil a litre or two.
Specific heat of common substances
| Substance | c, J/(kg·°C) | Energy to warm 1 kg by 25°C |
|---|---|---|
| Water | 4,184 | 104,600 J |
| Ethanol | 2,440 | 61,000 J |
| Air | 1,005 | 25,125 J |
| Aluminium | 900 | 22,500 J |
| Glass | 840 | 21,000 J |
| Steel | 490 | 12,250 J |
| Copper | 385 | 9,625 J |
| Lead | 130 | 3,250 J |
Water’s value stands out — nothing common comes close — which is why it’s the go-to coolant and thermal buffer.
Where the calculation is used
- Sizing heaters and coolers. How many watts to raise a tank of water by a set amount in a set time.
- Calorimetry. Measuring a reaction’s heat by the temperature change it causes in a known mass of water.
- HVAC and building physics. The thermal mass of concrete and masonry slows a building’s temperature swings.
- Cooking and food processing. Heating and chill-down times for large batches.
- Climate and oceanography. The ocean’s enormous heat capacity is why coastal climates are mild.
What the formula assumes
It assumes all the energy goes into the substance and none leaks to the container, the air, or the surroundings — which is never quite true. Real heating jobs need more energy than the bare
Common mistakes
- Mixing units — mass in grams with a c in J/(kg·°C) gives an answer 1,000× too small.
- Ignoring the container in a real heating calculation.
- Forgetting latent heat when the process crosses a melting or boiling point.
- Using a Celsius specific heat with a Kelvin temperature change — the size of a degree is the same, so ΔT is identical, but be consistent.
For thermodynamic work that also involves pressure–volume changes, see the enthalpy calculator.