Specific Heat Calculator
Calculate the heat needed to change the temperature of a mass of water, metal, air or another material — Q = m c ΔT — and how long a heater takes to supply it.
The energy to heat something up, and the time a kettle or heater needs.
How the specific heat calculator works
Heating a material takes energy in proportion to its mass, its specific heat capacity and the temperature change: Q = m c ΔT. Water has an unusually high specific heat (4,186 J/kg·K), which is why a kettle takes a while and why oceans moderate climate; metals need far less per kilogram.
Enter a heater power in Detailed mode and the calculator divides to give the heating time, assuming no losses — real kettles lose 10–20% to the surroundings.
Formula: Q = m c ΔT · t = Q ÷ P
Worked examples
| Inputs | Heat required | Note |
|---|---|---|
| 1.5 L of water from 20 to 100 °C | 502,320 J | 502 kJ — 3.8 min at 2.2 kW |
| 1 kg of aluminium by 100 °C | 89,700 J | 89.7 kJ |
| 60 kg of air (a room) by 5 °C | 301,500 J | 302 kJ |
FAQFrequently asked questions
What is specific heat capacity?
The energy needed to raize one kilogram of a material by one kelvin (one degree Celsius). Water's is 4,186 J/kg·K — among the highest of common substances.
Why does a kettle take longer than the calculator says?
Losses: heat escapes to the air and the kettle body, and the element is not 100% efficient. Add 10–20%.
Does the formula cover boiling?
No — changing phase takes latent heat with no temperature change: 2,260 kJ/kg to boil water, 334 kJ/kg to melt ice. Add it separately.
Is a kelvin change the same as a Celsius change?
Yes. The scales have the same step size; only the zero differs, and ΔT is a difference.
Where these figures come from
- NIST — CODATA 2018 fundamental physical constants — G, g₀, R, c
- NIST Special Publication 811 — Guide for the use of the International System of Units — unit conversions
- The Engineering ToolBox — material properties — specific heats, expansion coefficients, densities
- National Institute of Standards and Technology — the US measurement authority
Last checked: September 2026. Constants are the CODATA 2018 values; formulas are the standard textbook forms.